[PWGUD] addd true gap service and add TPC-FT0 correlations

[Luzhiyongg]

No description provided.

[github-actions]

O2 linter results: ❌ 1 errors, ⚠️ 15 warnings, 🔕 0 disabled

[alibuild]

Error while checking build/O2Physics/o2 for ebf4471 at 2026-05-04 14:02:

## sw/BUILD/O2Physics-latest/log
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGUD/Tasks/upcTrueGapService.cxx:58:81: error: unused parameter 'tracks' [-Werror=unused-parameter]
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGUD/Tasks/flowLongRangeCorrUpc.cxx:346:14: error: unused variable 'phi' [-Werror=unused-variable]
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGUD/Tasks/flowLongRangeCorrUpc.cxx:507:16: error: variable 'w2C' set but not used [-Werror=unused-but-set-variable]
ninja: build stopped: subcommand failed.

Full log here.

[alibuild]

Error while checking build/O2Physics/o2 for aaf8aa8 at 2026-05-04 14:04:

## sw/BUILD/O2Physics-latest/log
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGUD/Tasks/upcTrueGapService.cxx:59:81: error: unused parameter 'tracks' [-Werror=unused-parameter]
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGUD/Tasks/flowLongRangeCorrUpc.cxx:345:14: error: unused variable 'phi' [-Werror=unused-variable]
/sw/SOURCES/O2Physics/slc9_x86-64-slc9_x86-64/0/PWGUD/Tasks/flowLongRangeCorrUpc.cxx:504:16: error: variable 'w2C' set but not used [-Werror=unused-but-set-variable]
ninja: build stopped: subcommand failed.

Full log here.