feat: Add shutdown with timeout for metric exporter

[mohammadVatandoost]

#2574 Part 1: Adding shutdown_with_timeout for metric exporter

[codecov]

Codecov Report

Attention: Patch coverage is 16.66667% with 15 lines in your changes missing coverage. Please review.

Project coverage is 81.0%. Comparing base (99cb67d) to head (25156f0).

Files with missing lines	Patch %	Lines
opentelemetry-otlp/src/metric.rs	0.0%	3 Missing ⚠️
opentelemetry-sdk/src/metrics/exporter.rs	0.0%	3 Missing ⚠️
...pentelemetry-sdk/src/metrics/in_memory_exporter.rs	0.0%	3 Missing ⚠️
opentelemetry-sdk/src/metrics/periodic_reader.rs	50.0%	3 Missing ⚠️
opentelemetry-stdout/src/metrics/exporter.rs	0.0%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #2854     +/-   ##
=======================================
- Coverage   81.1%   81.0%   -0.1%     
=======================================
  Files        124     125      +1     
  Lines      23927   23945     +18     
=======================================
- Hits       19410   19409      -1     
- Misses      4517    4536     +19     

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[TommyCpp]

Is it from spec? If so please link the document here nvm I think we have it already, maybe worth following up to see if the value is reasonable

[mohammadVatandoost]

The 5 second is used in other functions as default timeout. like:

opentelemetry-rust/opentelemetry-sdk/src/trace/span_processor.rs

Line 425 in a071d8f

forceflush_timeout: Duration::from_secs(5), // TODO: make this configurable

I don't know why we choose 5 seconds. As it is written in ToDo, I think we need to read it from configuration.
I think this is not related to issue of the PR. we can work on it at another PR.

[cijothomas]

There is no spec on what should be the default, so 5 seconds is our invention. We should recommend users to use the shutdown_with_timeout passing a Duration of their choice, but we also do shutdown() from Drop, where we need to pick some default. 5 secs seems reasonable to me as a default.

[cijothomas]

now that we have both, lets give a default implementation for the shutdown(), invoking the new one passing 5 seconds.

Also please update changelog to reflect this - this is breaking change for custom MetricExporter author.

[mohammadVatandoost]

Done