[WIP]ForceFlush before cancling the running requests when shutdown.

[owent]

Fixes #2715

Changes

• ForceFlush before shutdown in OTLP exporters.

Sorry for having no time to test yet, I will test it next week when I have time

For significant contributions please make sure you have completed the following items:

• [ ] CHANGELOG.md updated for non-trivial changes
• [ ] Unit tests have been added
• [x] Changes in public API reviewed

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.66%. Comparing base (497eaf4) to head (733b7a0). Report is 106 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2727      +/-   ##
==========================================
+ Coverage   87.12%   87.66%   +0.55%     
==========================================
  Files         200      190      -10     
  Lines        6109     5858     -251     
==========================================
- Hits         5322     5135     -187     
+ Misses        787      723      -64     

see 120 files with indirect coverage changes