fix: cleanup MetricError

[cijothomas]

Continuing from #2905

There will be further cleanups for MetricError to the point it'll be completely removed. All places where it is required has been modified to use the OTelSdkResult. The remaining usages are only required for "Views", which is experimental features, so the MetricError can remain public only when that feature is enabled, otherwise non-public.
This helps cleanup unnecessary public API from the Metrics Sdk, and gets one more step closer to declaring Metrics Sdk as stable.

[codecov]

Codecov Report

Attention: Patch coverage is 11.11111% with 8 lines in your changes missing coverage. Please review.

Project coverage is 81.3%. Comparing base (df26240) to head (c069493).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
opentelemetry-otlp/src/exporter/http/mod.rs	0.0%	6 Missing ⚠️
opentelemetry-otlp/src/exporter/http/metrics.rs	0.0%	2 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #2906   +/-   ##
=====================================
  Coverage   81.3%   81.3%           
=====================================
  Files        126     126           
  Lines      24256   24253    -3     
=====================================
  Hits       19735   19735           
+ Misses      4521    4518    -3     

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[gruebel]

nice

[gruebel]

shouldn't this be internal-logs feature?

[cijothomas]

no, this is only used when json serialization failed, and it was complaining about unused imports without this!