[#25501] Stabilize flaky Fast DDS Spy Windows application tests in CI

[Danipiza]

Description

This PR reduces flakiness in the Fast DDS Spy application tests on Windows CI.

GitHub Actions on windows-2022 was showing flaky failures in Fast DDS Spy application tests that do not reproduce reliably locally. The failures were concentrated in DDS discovery-dependent one-shot tests

Changes

• Add a short startup delay before launching the spy when DDS publisher-based tests are used
• Increase the shared discovery time used by DDS-backed application tests
• Normalize empty CLI output so '' and '\n' are treated equivalently
• Improve one-shot test diagnostics by printing stderr on timeout

[codecov]

Codecov Report

❌ Patch coverage is 78.57143% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.08%. Comparing base (1c51730) to head (04fcba7).

Files with missing lines	Patch %	Lines
fastddsspy_tool/src/cpp/tool/Controller.cpp	78.57%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #152      +/-   ##
==========================================
- Coverage   62.82%   58.08%   -4.74%     
==========================================
  Files          29       28       -1     
  Lines        2480     1942     -538     
  Branches     1068      773     -295     
==========================================
- Hits         1558     1128     -430     
+ Misses        363      330      -33     
+ Partials      559      484      -75     

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[Danipiza]

Closing PR, reopening in #154 with a different branch name