Add few internal logs for Metrics sdks

[cijothomas]

Modified self-diag example to not do anything invalid to trigger logs, as we have sufficient logs otherwise to demonstrate!
Also few logs inside Metric sdk.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 10 lines in your changes missing coverage. Please review.

Project coverage is 79.5%. Comparing base (91370d2) to head (76f57ff).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
opentelemetry-sdk/src/metrics/meter_provider.rs	53.3%	7 Missing ⚠️
opentelemetry-sdk/src/metrics/pipeline.rs	50.0%	2 Missing ⚠️
opentelemetry-sdk/src/metrics/periodic_reader.rs	0.0%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #2350     +/-   ##
=======================================
- Coverage   79.5%   79.5%   -0.1%     
=======================================
  Files        123     123             
  Lines      21366   21379     +13     
=======================================
+ Hits       17000   17001      +1     
- Misses      4366    4378     +12     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[utpilla]

Left some suggestions.