SonicTriton: implement RetryActionDiffServer via TritonService; add tests and cfg support

[trevin-lee]

PR description:

• Implement RetryActionDiffServer for SonicTriton using TritonService’s server registry; remove per-action alternate server parameters.
• Use TritonClient::updateServer(TritonService::Server::fallbackName) to switch servers on retry, per review guidance.
• Extend test coverage:
  • Add Catch2 unit test HeterogeneousCore/SonicTriton/test/test_RetryActionDiffServer.cc (arms → updateServer(fallback) → no-op on second retry → exception path is caught).
  • Extend HeterogeneousCore/SonicTriton/test/tritonTest_cfg.py with --retryAction {same,diff} and a verbose confirmation line.
  • Add scripted test TestHeterogeneousCoreSonicTritonRetryActionDiff_Log to assert the selected retry policy.
• Move all test definitions to HeterogeneousCore/SonicTriton/test/BuildFile.xml (remove package-level test entries; use proper <bin> with catch2).
• Provide a protected default constructor for TritonClient (test double support), removing the unused testing flag constructor.
• Aligns with the Retry framework expectations discussed in review (ref: “Test PR for new Retry Framework Test PR for new Retry Framework #19”); no physics changes expected, functionality is exercised only when retry is configured.

PR validation:

• Built and ran unit/integration tests in a fresh CMSSW_15_1_0_pre3 area:
  • scram b -j 8
  • scram b runtests TEST=HeterogeneousCore/SonicTriton (passes)
• Catch2 test validates action behavior; cmsRun-based tests validate configuration wiring for both same and diff policies.
• No changes to standard workflows unless Client.Retry is explicitly configured.

Backport:

• Not a backport. If needed, a follow-up backport can be proposed for CMSSW_15_0_X after this PR is reviewed.

[kpedro88]

@trevin-lee I've updated the master branch to synchronize with upstream cmssw now, but you may have to remake the PR (GitHub sometimes doesn't update correctly)