[PWGDQ] Adding new process function for electron-muon analysis

[Shunsuke-Kurita]

This PR implements processElectronMuonDirect in AnalysisSameEventPairing for direct electron-muon pairing on AO2D tracks, completing the tableReader_withAssoc_direct workflow for EMu analyses. To support this, it also adds processDirectWithFilter to AnalysisEventSelection — enabling filterPPwithAssociation as an upstream pre-filter — and introduces a new AnalysisMuonSelection struct for direct muon selection on AO2D FwdTracks.

[vkucera]

@Shunsuke-Kurita Your PR fails the compilation and the formatting. Please test your changes before making a PR.

[alibuild]

Error while checking build/O2Physics/o2 for 189bde2 at 2026-03-23 12:36:

## sw/BUILD/O2Physics-latest/log
/sw/SOURCES/O2Physics/15490-slc9_x86-64/0/PWGDQ/Tasks/tableReader_withAssoc_direct.cxx:1315:40: error: unused parameter 'events' [-Werror=unused-parameter]
/sw/SOURCES/O2Physics/15490-slc9_x86-64/0/PWGDQ/Tasks/tableReader_withAssoc_direct.cxx:1997:110: error: unused parameter 'tracks1' [-Werror=unused-parameter]
/sw/SOURCES/O2Physics/15490-slc9_x86-64/0/PWGDQ/Tasks/tableReader_withAssoc_direct.cxx:1998:107: error: unused parameter 'tracks2' [-Werror=unused-parameter]
ninja: build stopped: subcommand failed.

Full log here.

[Shunsuke-Kurita]

Dear @vkucera ,
Thank you for your feedback.
The code compiles successfully in my local environment, and I have also tested that the newly added process function works as expected.
However, I see that there are compilation errors in the CI. I will check the issues and update the code accordingly.
Thank you for pointing this out.

[alibuild]

Error while checking build/O2Physics/o2 for efabcf7 at 2026-03-26 18:06:

## sw/BUILD/O2Physics-latest/log
c++: fatal error: Killed signal terminated program cc1plus
c++: fatal error: Killed signal terminated program cc1plus
ninja: build stopped: subcommand failed.

Full log here.