Make a common Error enum for export shutdown and flush operations

[cijothomas]

As discussed https://github.com/open-telemetry/opentelemetry-rust/pull/2600/files#r1941764809 this renames the ShutdownError to OTelSdkError
ShutdownResult to OTelSdkResult

In separate follow up PR, we can modify usages to move to the new one, and finally do the removal of existing Errors types

[codecov]

Codecov Report

Attention: Patch coverage is 56.75676% with 16 lines in your changes missing coverage. Please review.

Project coverage is 79.2%. Comparing base (b017c7b) to head (6c77dee).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
opentelemetry-sdk/src/metrics/manual_reader.rs	0.0%	5 Missing ⚠️
opentelemetry-sdk/src/metrics/periodic_reader.rs	70.0%	3 Missing ⚠️
opentelemetry-otlp/src/exporter/http/metrics.rs	0.0%	2 Missing ⚠️
opentelemetry-otlp/src/exporter/tonic/metrics.rs	0.0%	2 Missing ⚠️
opentelemetry-otlp/src/metric.rs	0.0%	1 Missing ⚠️
.../src/metrics/periodic_reader_with_async_runtime.rs	85.7%	1 Missing ⚠️
opentelemetry-sdk/src/metrics/pipeline.rs	66.6%	1 Missing ⚠️
opentelemetry-stdout/src/metrics/exporter.rs	0.0%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #2603     +/-   ##
=======================================
- Coverage   79.2%   79.2%   -0.1%     
=======================================
  Files        118     118             
  Lines      22503   22504      +1     
=======================================
  Hits       17829   17829             
- Misses      4674    4675      +1     

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[lalitb]

Looks good to me.
nit - OTelSdk{Result}/Error -> Sdk{Result}/Error as opentelemetry is already part of namespace. But no strong opinion.

[cijothomas]

Looks good to me. nit - OTelSdk{Result}/Error -> Sdk{Result}/Error as opentelemetry is already part of namespace. But no strong opinion.

Will merge as-is. After every other change, lets us make a call on that and rename. (I like your suggestion to avoid repeating OTel given it is already in namespace.)