[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.