Add script to diff zjit stats from output csv

Example output:

================================================================================
ZJIT Stats Comparison
================================================================================

  ruby-mdev (baseline):
    ruby 4.1.0dev (2026-01-30T17:29:15Z master 1298f9ac1a) +ZJIT dev +PRISM [arm64-darwin25]
  ruby-bdev:
    ruby 4.1.0dev (2026-01-30T17:29:15Z profile-block-arg 1298f9ac1a) +ZJIT dev +PRISM [arm64-darwin25]

BENCHMARK TIMINGS (lower is better)
--------------------------------------------------------------------------------
  lobsters:
    ruby-mdev            avg:   1.076s  min:   0.944s  ★ (baseline)
    ruby-bdev            avg:   1.103s  min:   0.967s       +2.5% (slower)
  railsbench:
    ruby-mdev            avg:   1.580s  min:   1.532s  ★ (baseline)
    ruby-bdev            avg:   1.587s  min:   1.539s       +0.4% (slower)

MEMORY USAGE
--------------------------------------------------------------------------------
  lobsters:
    ruby-mdev            maxrss:    510.3MB  zjit_mem:     65.9MB
    ruby-bdev            maxrss:    510.6MB  zjit_mem:     65.5MB
  railsbench:
    ruby-mdev            maxrss:    200.2MB  zjit_mem:     30.1MB
    ruby-bdev            maxrss:    203.9MB  zjit_mem:     29.8MB

NOT INLINED C METHODS (showing differences > 10.0%)
--------------------------------------------------------------------------------
  lobsters:
    #<Module:0x000000012a06a460>#object_id           241 →              0 ▼ -100.0%
    Kernel#instance_variable_defined?                416 →              8 ▼  -98.1%
    Numeric#nonzero?                               9,789 →          1,556 ▼  -84.1%
    ... and 11 more
  railsbench:
    Array#hash                                      133 →            285 ▲ +114.3%
    #<Module:0x000000012804a500>#enum_for           180 →              0 ▼ -100.0%
    String#<=>                                    9,896 →          1,674 ▼  -83.1%
    ... and 10 more

CALLS TO C FUNCTIONS FROM JIT CODE (showing differences > 10.0%)
--------------------------------------------------------------------------------
  lobsters:
    #<Module:0x000000012a06a460>#object_id           241 →              0 ▼ -100.0%
    Kernel#instance_variable_defined?                416 →              8 ▼  -98.1%
    Class#new                                        561 →             22 ▼  -96.1%
    ... and 18 more
  railsbench:
    Array#hash                                      133 →            285 ▲ +114.3%
    #<Module:0x000000012804a500>#enum_for           180 →              0 ▼ -100.0%
    Numeric#nonzero?                              9,896 →          1,674 ▼  -83.1%
    ... and 15 more

NOT OPTIMIZED METHOD TYPES FOR SEND (showing differences > 10.0%)
--------------------------------------------------------------------------------
  lobsters:
    optimized                                       0 →          4,591 ▲    new
  railsbench:
    optimized                                  19,471 →         49,608 ▲ +154.8%

NOT OPTIMIZED METHOD TYPES FOR SUPER (showing differences > 10.0%)
--------------------------------------------------------------------------------
  lobsters:
    attrset                                     2,642 →          1,866 ▼  -29.4%

SEND FALLBACK REASONS (showing differences > 10.0%)
--------------------------------------------------------------------------------
  lobsters:
    send_not_optimized_method_type              1,682 →          6,273 ▲ +272.9%
    one_or_more_complex_arg_pass            1,145,141 →      2,821,156 ▲ +146.4%
    send_no_profiles                        2,068,333 →        196,661 ▼  -90.5%
    ... and 3 more
  railsbench:
    send_not_optimized_method_type             19,471 →         49,608 ▲ +154.8%
    one_or_more_complex_arg_pass            2,641,602 →      4,786,718 ▲  +81.2%
    send_no_profiles                        4,046,018 →      1,069,740 ▼  -73.6%
    ... and 1 more

SETIVAR FALLBACK REASONS (showing differences > 10.0%)
--------------------------------------------------------------------------------
  lobsters:
    new_shape_needs_extension                     946 →            170 ▼  -82.0%
  railsbench:
    new_shape_needs_extension                     935 →            161 ▼  -82.8%

GETBLOCKPARAMPROXY HANDLER (showing differences > 10.0%)
--------------------------------------------------------------------------------
  railsbench:
    no_profiles                                 1,146 →            350 ▼  -69.5%

COMPLEX ARGUMENT-PARAMETER FEATURES (showing differences > 10.0%)
--------------------------------------------------------------------------------
  lobsters:
    caller_blockarg                            21,564 →      1,697,716 ▲+7772.9%
    caller_kwarg                               23,322 →        135,011 ▲ +478.9%
    caller_splat                               33,663 →         37,288 ▲  +10.8%
  railsbench:
    caller_kwarg                                  944 →        110,104 ▲+11563.6%
    caller_blockarg                           184,024 →      2,329,272 ▲+1165.7%
    caller_splat                              170,800 →        260,718 ▲  +52.6%

SIDE EXIT REASONS (showing differences > 10.0%)
--------------------------------------------------------------------------------
  lobsters:
    obj_to_string_fallback                      1,948 →            443 ▼  -77.3%
  railsbench:
    obj_to_string_fallback                      2,021 →            370 ▼  -81.7%

NOT ANNOTATED C METHODS (showing differences > 10.0%)
--------------------------------------------------------------------------------
  lobsters:
    #<Module:0x000000012a06a460>#object_id           241 →              0 ▼ -100.0%
    Class#new                                        561 →             22 ▼  -96.1%
    String#<=>                                     9,789 →          1,556 ▼  -84.1%
    ... and 10 more
  railsbench:
    Array#hash                                      133 →            285 ▲ +114.3%
    #<Module:0x000000012804a500>#enum_for           180 →              0 ▼ -100.0%
    Numeric#nonzero?                              9,896 →          1,674 ▼  -83.1%
    ... and 11 more

Author: rwstauner