[Trigger,PWGUD] DPL Analysis: use API instead of direct construction

[aalkin]

This is needed for the upcoming update in O2 that will make creating table slices more performant

[github-actions]

O2 linter results: ❌ 5 errors, ⚠️ 3 warnings, 🔕 0 disabled

[alibuild]

Error while checking build/O2Physics/code-check for 3f41f1c at 2026-07-09 14:53:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 8 errors and 0 warnings.'
Found 8 errors and 0 warnings.
++ [[ 8 -gt 0 ]]
++ cat /sw/BUILD/cb7a3d163c0dfe4f78ab6403aff70523a5b91401/O2Physics-code-check/errors.txt
EventFiltering/PWGUD/diffractionBCFilter.cxx:86:14: error: variable 'closestBC' is not initialized [cppcoreguidelines-init-variables,-warnings-as-errors]
EventFiltering/PWGUD/diffractionBCFilter.cxx:139:9: error: variable 'indBCToSave' is not initialized [cppcoreguidelines-init-variables,-warnings-as-errors]
EventFiltering/PWGUD/diffractionBCFilter.cxx:142:11: error: the 'empty' method should be used to check for emptiness instead of 'size' [readability-container-size-empty,-warnings-as-errors]
EventFiltering/PWGUD/diffractionBCFilter.cxx:223:9: error: variable 'indBCToSave' is not initialized [cppcoreguidelines-init-variables,-warnings-as-errors]
EventFiltering/PWGUD/diffractionBCFilter.cxx:226:11: error: the 'empty' method should be used to check for emptiness instead of 'size' [readability-container-size-empty,-warnings-as-errors]
EventFiltering/PWGUD/diffractionBCFilter.cxx:255:29: error: initializer for member 'diffCuts' is redundant [readability-redundant-member-init,-warnings-as-errors]
EventFiltering/PWGUD/diffractionBCFilter.cxx:323:9: error: variable 'isDGBC' is not initialized [cppcoreguidelines-init-variables,-warnings-as-errors]
EventFiltering/PWGUD/diffractionBCFilter.cxx:324:15: error: loop variable is copied but only used as const reference; consider making it a const reference [performance-for-range-copy,-warnings-as-errors]
++ [[ 0 -gt 0 ]]
++ [[ 8 -gt 0 ]]
++ exit 1
--

Full log here.