logs: add test for invalid OTEL_BLRP_SCHEDULE_DELAY env value

[MPSAJID]

This PR adds a unit test covering the behavior when OTEL_BLRP_SCHEDULE_DELAY
is set to an invalid value.

Invalid values are logged with a warning and the default schedule delay
(1000ms) is used. The new test documents and locks in this fallback behavior
to reduce the risk of future regressions.

Related to #3806 .

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: MPSAJID / name: Sajid Husain Patil (0cabb8e)

[lalitb]

LGTM. This covers the non-parseable string case. If the intent is to validate overall robustness of OTEL_BLRP_SCHEDULE_DELAY, it might also be worth adding cases for negative values, zero, overflow, malformed units, or an empty string.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.96%. Comparing base (2868dd1) to head (0cabb8e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3811      +/-   ##
==========================================
+ Coverage   89.94%   89.96%   +0.02%     
==========================================
  Files         225      225              
  Lines        7167     7167              
==========================================
+ Hits         6446     6447       +1     
+ Misses        721      720       -1     

see 1 file with indirect coverage changes

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[MPSAJID]

Thanks for the review!

Agreed ,those are good additional cases to cover. I’ll follow up with a separate PR to extend coverage for other invalid values.