[EXAMPLES] Deprecated semantic conventions used

[marcalff]

Fixes #3890

Changes

Please provide a brief description of the changes here.

• In metrics_foo_library, use non deprecated semantic conventions as example
• In the grpc example, use proper rpc semantic conventions

This resolves deprecation warnings related to old semantic conventions.

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

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.07%. Comparing base (6eb0e1f) to head (ac88311).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3905   +/-   ##
=======================================
  Coverage   90.07%   90.07%           
=======================================
  Files         226      226           
  Lines        7217     7217           
=======================================
  Hits         6500     6500           
  Misses        717      717           

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