Per-StressTest fault injection with env/fs cleanup

[hx235]

Summary:
Prerequisite for multi-DB stress test support where each StressTest instance owns one DB. Moves fault injection from a single global to per-StressTest instance so each DB gets isolated fault injection — errors injected into one DB do not leak to others.

FS/Env architecture change:

Before (upstream):
raw_fs → FaultInjectionTestFS (global) → DbStressFSWrapper → db_stress_env → DB::Open

After (this diff):
Global: raw_env (no wrappers)
Used outside StressTest: non-FS ops (threads, time, sleep), test framework FS setup (dirs), DB destruction
Used inside StressTest: cleanup ops that must succeed (external file delete)

Per StressTest:
  raw_fs → DbStressFSWrapper (db_stress_fs_, always)
            → FaultInjectionTestFS (db_fault_injection_fs_, optional)
                  → CompositeEnvWrapper (db_env_, always) → DB::Open

Expected values state: Env::Default() (always local PosixEnv even when raw_env is remote)

FS layer order swapped (DbStressFSWrapper now innermost). Safe because:

• Error injection returns early — inner wrapper never executes (same behavior)
• DbStressFSWrapper assertions do not modify data (checksum validation, IOActivity checks)
• MANIFEST rename tracking slightly better for crash simulation in new order

Stored members (per StressTest):

• db_stress_fs_: DbStressFSWrapper. Always active regardless of fault injection flags.
• db_fault_injection_fs_: FaultInjectionTestFS. Only when fault injection flags set. Direct access for Enable/Disable/SetThreadLocal.
• db_env_: CompositeEnvWrapper. Always present. THE env for all DB I/O (options_.env).

Eliminated globals: db_stress_env → renamed to raw_env (no wrappers, DbStressFSWrapper moved to per-StressTest); db_stress_listener_env, db_stress_raw_fs removed; fault_fs_guard, fault_env_guard moved to per-StressTest.

Other changes:

• CleanupOutputDirectory simplified (uses raw_env, no disable/enable needed)
• SstFileManager recreated with per-StressTest env in Open()
• Remote compaction override env uses options.env directly (fixes pre-existing silent bug)
• Comments added: Env::Default() always local, DbStressDestroyDb MANIFEST explanation, fault injection log path in TEST_TMPDIR

Differential Revision: D104959945

[meta-codesync]

@hx235 has exported this pull request. If you are a Meta employee, you can view the originating Diff in D104959945.

[github-actions]

⚠️ clang-tidy: 6 warning(s) on changed lines

Completed in 155.3s.

Summary by check

Check	Count
concurrency-mt-unsafe	2
cppcoreguidelines-avoid-non-const-global-variables	4
Total	6

Details

db_stress_tool/db_stress_common.cc (2 warning(s))

db_stress_tool/db_stress_common.cc:22:25: warning: variable 'raw_env' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables]
db_stress_tool/db_stress_common.cc:22:25: warning: variable 'raw_env' provides global access to a non-const object; consider making the pointed-to data 'const' [cppcoreguidelines-avoid-non-const-global-variables]

db_stress_tool/db_stress_test_base.cc (2 warning(s))

db_stress_tool/db_stress_test_base.cc:128:31: warning: function is not thread safe [concurrency-mt-unsafe]
db_stress_tool/db_stress_test_base.cc:3883:7: warning: function is not thread safe [concurrency-mt-unsafe]

db_stress_tool/db_stress_tool.cc (2 warning(s))

db_stress_tool/db_stress_tool.cc:39:49: warning: variable 'fault_fs_for_crash_report' is non-const and globally accessible, consider making it const [cppcoreguidelines-avoid-non-const-global-variables]
db_stress_tool/db_stress_tool.cc:39:49: warning: variable 'fault_fs_for_crash_report' provides global access to a non-const object; consider making the pointed-to data 'const' [cppcoreguidelines-avoid-non-const-global-variables]