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]

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Name	Link
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.83%. Comparing base (497eaf4) to head (19d20cf).
Report is 142 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3104      +/-   ##
==========================================
+ Coverage   87.12%   87.83%   +0.71%     
==========================================
  Files         200      195       -5     
  Lines        6109     5969     -140     
==========================================
- Hits         5322     5242      -80     
+ Misses        787      727      -60     

see 125 files with indirect coverage changes