[EXPORTER] Add config options to prometheus exporter

[psx95]

Fixes #2453

Changes

Added the following optional configuration options (booleans) to the prometheus exporter:

• without_units : controls whether to add unit suffixes (e.g. _seconds) to the metric names.
• without_type_suffix: controls whether to add type suffixes (e.g. _total) to the metric names.

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

[netlify]

✅ Deploy Preview for opentelemetry-cpp-api-docs canceled.

Name	Link
🔨 Latest commit	0f75727
🔍 Latest deploy log	https://app.netlify.com/sites/opentelemetry-cpp-api-docs/deploys/67156e23a6204800088d7273

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.91%. Comparing base (497eaf4) to head (0f75727).
Report is 144 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3104      +/-   ##
==========================================
+ Coverage   87.12%   87.91%   +0.79%     
==========================================
  Files         200      195       -5     
  Lines        6109     6133      +24     
==========================================
+ Hits         5322     5391      +69     
+ Misses        787      742      -45     

see 98 files with indirect coverage changes

[lalitb]

Thanks.

[marcalff]

Thanks for the fix.

Please fix minor comments on the code flow.
Will approve after that.

[psx95]

Thanks for the reviews! I made the requested changes.

I sometimes find double negatives in if conditions a little unreadable, hopefully the small comments on top would make things clear.

[marcalff]

LGTM, thanks for the fix.