[Nexthop] Extend buck_cmake_dep_checker to catch file-list inconsistencies.

[benoit-nexthop]

Summary

Extends fboss/oss/scripts/buck_cmake_dep_checker.py with two new check modes and several bug fixes.

New flags

  --check-files               cmake → BUCK direction; files in cmake must
                              also appear in some BUCK target
  --check-files --from-commit REF [--to-commit REF]
                              Bidirectional check for files changed in the
                              given commit range; any touched .cpp must be
                              in both build systems
  --check-sorted              Check that srcs/headers file lists in BUCK and
                              cmake targets are sorted alphabetically
  --check-sorted --from-commit REF
                              Limit the sort check to targets defined in
                              build files (BUCK/*.cmake) touched by the
                              commit range — avoids flooding output with
                              pre-existing violations in unrelated targets

--check-files and --check-sorted can be combined; they share one parse pass:

  buck_cmake_dep_checker.py --check-files --check-sorted --from-commit HEAD~

The pre-commit hook in .pre-commit-config.yaml is updated to use this combined invocation.

Design choices (file-list check)

• Same-name 1:1 target pairing with >0 shared .cpp as confidence gate (excludes macro/glob-generated Buck targets invisible to the parser)
• Name normalization: cmake uses underscores (fboss2_config_lib) while BUCK uses hyphens (fboss2-config-lib); both sides are normalized before matching so the confidence gate works correctly
• Buck headers lists are included in the global corpus (some .cpp files live under headers in BUCK, not srcs); previously these appeared as false-positive "missing from BUCK" entries
• Files under oss/ or facebook/ path segments silently skipped (OSS shims)
• Only paths starting with fboss/ considered

Also fixes a pre-existing parser bug

• cpp_library/thrift_library blocks with comments between ( and name = were silently skipped; fixed by extracting the block first then searching for name= inside it (21 additional targets now parsed)

Test Plan

Tested against #1140 (config/delete tunnel ip-in-ip). With --from-commit, output is scoped to the 6 build files touched by that commit:

$ buck_cmake_dep_checker.py --check-files --check-sorted --from-commit 8caf0fc^

FILE LIST INCONSISTENCIES (changed files 8caf0fc^..HEAD)
================================================================================
No file list inconsistencies found!

FILE LIST SORT ORDER VIOLATIONS
================================================================================

fboss/cli/fboss2/test/config/BUCK:
  [buck] //fboss/cli/fboss2/test/config:cmd_config_test  (srcs)
    First unsorted entry at position 17: 'CmdConfigVlanDefaultTest.cpp'
    (expected 'CmdConfigTunnelIpInIpTest.cpp')

The CmdConfigTunnelIpInIpTest.cpp (T) was appended after CmdConfigVlanDefaultTest.cpp (V); alphabetically T < V so the test file should appear first.

Also validated against #1095 where --check-files --from-commit correctly flagged two integration test files added to BUCK but missing from cmake:

================================================================================
FILE LIST INCONSISTENCIES (changed files HEAD~1..HEAD)
================================================================================

In BUCK but missing from cmake:
  fboss/cli/fboss2/test/integration_test/ConfigInterfaceIpv6NdpTest.cpp
    Buck target: //fboss/cli/fboss2/test/integration_test:fboss2_integration_test
    Buck file:   /var/FBOSS/fboss/fboss/cli/fboss2/test/integration_test/BUCK
  fboss/cli/fboss2/test/integration_test/DeleteInterfaceIpv6NdpTest.cpp
    Buck target: //fboss/cli/fboss2/test/integration_test:fboss2_integration_test
    Buck file:   /var/FBOSS/fboss/fboss/cli/fboss2/test/integration_test/BUCK