[improvement](be) Add disk cache for external file metadata

[xylaaaaa]

What problem does this PR solve?

Issue Number: N/A

Related PR: N/A

Problem Summary:
External Parquet/ORC footer metadata was only cached in BE memory. After memory cache eviction or BE restart, repeated reads from remote storage such as S3/HDFS had to fetch footer metadata remotely again. This PR adds a disk-backed L2 cache for external file metadata by reusing the file cache META queue, and wires it into Parquet/ORC readers with separate profile counters for memory and disk hits.

Main changes:

• Add enable_external_file_meta_disk_cache and external_file_meta_disk_cache_percent BE configs.
• Add FileMetaDiskCache serialization and validation for Parquet/ORC footer payloads.
• Add a META file-cache queue and eviction behavior that prefers evicting data cache before metadata cache.
• Add Parquet/ORC reader profile counters split into memory/disk hit and disk miss/write counters.
• Allow metadata disk cache initialization without enabling data file cache.

Release note

Add optional disk-backed external file metadata cache for Parquet/ORC readers.

Check List (For Author)

• Test: Unit Test / Manual test
  • PATH=/mnt/disk1/chenjunwei/doris_tools/ldb_toolchain_llvm16/bin:$PATH CLANG_FORMAT_BINARY=/mnt/disk1/chenjunwei/doris_tools/ldb_toolchain_llvm16/bin/clang-format build-support/check-format.sh passed.
  • git diff --check origin/master...HEAD passed.
  • Added BE UT coverage for file meta disk cache read/write, META queue eviction priority, read-only cache lookup, cache path meta percent parsing, and metadata cache initialization when enable_file_cache=false.
  • Attempted ./run-be-ut.sh --run --filter='FileMetaCacheTest.*:FileMetaDiskCacheTest.*:BlockFileCacheTest.file_cache_path_storage_parse:BlockFileCacheTest.file_meta_disk_cache_initializes_without_data_file_cache:BlockFileCacheTest.meta_queue_can_evict_data_cache_first:BlockFileCacheTest.normal_queue_does_not_evict_meta_cache:BlockFileCacheTest.read_if_cached_returns_downloaded_meta_block' -j 8; local worktree failed before running tests because thirdparty/installed/lib64/libaws-cpp-sdk-kinesis.a is missing for current master's BE UT link target.
  • Manual Parquet local TVF smoke test with enable_file_cache=false and enable_external_file_meta_disk_cache=true: cold query wrote disk cache, same-process hot query hit memory cache, BE restart hot query hit disk cache (FileFooterHitDiskCache=1, FileFooterReadCalls=0).
  • Manual ORC local TVF smoke test with the same config: cold query wrote disk cache, same-process hot query hit memory cache, BE restart hot query hit disk cache (FileFooterHitDiskCache=1, FileFooterReadCalls=0).
• Behavior changed: Yes. When enable_external_file_meta_disk_cache is true, external Parquet/ORC footer metadata can persist in local file cache and be reused after memory eviction or BE restart; this can be enabled independently from data file cache.
• Does this need documentation: Yes. Config documentation should describe enable_external_file_meta_disk_cache and external_file_meta_disk_cache_percent.

[hello-stephen]

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1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
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4. Which code was refactored and why was this part of the code refactored?
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[xylaaaaa]

Addressed the actionable review feedback in 92eab4fce4b:\n\n- Fixed ORC footer ownership on disk-cache hit and remote-read paths by keeping the payload in std::unique_ptr until the in-memory cache takes ownership.\n- Applied external_file_meta_disk_cache_percent to legacy four-field file_cache_path configs when metadata disk cache is enabled, and added BE UT coverage for that case.\n- Added the read_if_cached lifetime comment for the lockless read after collecting FileBlockSPtr references.\n- Fixed the historical INDEX/DISPOSABLE evict-size bvar label mismatch by indexing metrics with FileCacheType.\n\nNot changed in this patch: the Parquet raw-footer-byte split is a follow-up performance optimization; current reserialize path is correct but has extra CPU on first miss. I also rechecked the hit counters and current disk_cache() raw pointer usage; no code change needed there for the current stateless implementation.\n\nLocal verification:\n- build-support/check-format.sh\n- git diff --check\n- Tried ./run-be-ut.sh --run --filter=BlockFileCacheTest.file_cache_path_storage_parse -j 8, but local linking failed before test execution because thirdparty/installed/lib64/libaws-cpp-sdk-kinesis.a is missing.