Use dedicated ShutdownResult for Metric SDK shutdown

[cijothomas]

Trying to check how the changes discussed in
#2571 and #2564 would look like.
This touches just Metrics's Shutdown path.

[codecov]

Codecov Report

Attention: Patch coverage is 51.02041% with 24 lines in your changes missing coverage. Please review.

Project coverage is 79.6%. Comparing base (b50da91) to head (8ab63bf).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
opentelemetry-otlp/src/exporter/http/metrics.rs	0.0%	5 Missing ⚠️
opentelemetry-otlp/src/exporter/tonic/metrics.rs	0.0%	5 Missing ⚠️
opentelemetry-sdk/src/metrics/manual_reader.rs	0.0%	4 Missing ⚠️
opentelemetry-sdk/src/metrics/periodic_reader.rs	62.5%	3 Missing ⚠️
opentelemetry-sdk/src/metrics/pipeline.rs	40.0%	3 Missing ⚠️
.../src/metrics/periodic_reader_with_async_runtime.rs	85.7%	2 Missing ⚠️
opentelemetry-otlp/src/metric.rs	0.0%	1 Missing ⚠️
opentelemetry-stdout/src/metrics/exporter.rs	0.0%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #2573     +/-   ##
=======================================
- Coverage   79.6%   79.6%   -0.1%     
=======================================
  Files        118     118             
  Lines      22473   22486     +13     
=======================================
+ Hits       17902   17906      +4     
- Misses      4571    4580      +9     

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[scottgerring]

This LGTM and follows from our extensive discussions !
if you manage to merge it before the weekend, I could quickly do trace/logger Monday morning.

[cijothomas]

Thanks @scottgerring . @lalitb could you do another review?

[lalitb]

Nicely done. Thanks.

[cijothomas]

This LGTM and follows from our extensive discussions ! if you manage to merge it before the weekend, I could quickly do trace/logger Monday morning.

I'll continue to work on Metrics area only, to avoid conflicts, so you can do logs/trace side.