[Metrics] Revisit every public Error enums and Results

[cijothomas]

https://github.com/open-telemetry/opentelemetry-rust/blob/main/opentelemetry-sdk/src/metrics/error.rs#L13 defines pub enums that consist of errors from a variety of scenarios. The same is used as return type for export(), flush(), shutdown() methods, and also for internal validation methods for Views.

Must redesign this to ensure specific Error types are used for each methods.

Already discussed similar idea in #2381, but this issue is specifically for fixing Metrics.

[cijothomas]

The MeterProvider/Reader/Exporter is modified to use the newly added https://github.com/open-telemetry/opentelemetry-rust/blob/main/opentelemetry-sdk/src/error.rs

Views uses different one, that need to addressed before stabilizing it.
Additionally OTLP Exporter builder() also need modifications to the Result it returns.
Given the core work is completed, removing from 0.28 milestone..

[cijothomas]

#2905
#2928
#2906

These PRs did the most cleanup. Only remaining item is the struct passed to exporters, which is being refactored here: #2921

Closing as there is no pending tasks for this.