chore: Simplify generate.sh by removing git worktree and using generator-based check

[Not-Dhananjay-Mishra]

Added -check (env-driven via CHECK=1) support to:

• gen-accessors.go
• gen-iterators.go
• gen-stringify-test.go

Simplified script/generate.sh to:

• run go generate ./...
• optionally enable check mode via CHECK=1

Related : #3983

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.71%. Comparing base (88c87d1) to head (d1e963c).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4120   +/-   ##
=======================================
  Coverage   93.71%   93.71%           
=======================================
  Files         211      211           
  Lines       19614    19614           
=======================================
  Hits        18382    18382           
  Misses       1034     1034           
  Partials      198      198           

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[alexandear]

LGTM