Add support for LowMemory metrics temporality

[lalitb]

Fixes #2233

Changes

This PR adds a new AggregationTemporalitySelector for LowMemory with mapping between instrument types and aggregation temporality.

This is a BREAKING change for OTLP metrics exporter configuration, as OtlpHttpMetricExporterOptions and OtlpGrpcMetricExporterOptions class now use exporter::otlp::PreferredAggregationTemporality instead of sdk::metrics::AggregationTemporality as member. We could have instead kept both the fields to avoid this breaking change, but felt this is cleaner approach, unless there are other thoughts.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #2234 (f30e0dc) into main (bc23e6a) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

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  Coverage   87.31%   87.31%           
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  Files         169      169           
  Lines        4900     4900           
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  Hits         4278     4278           
  Misses        622      622           

[marcalff]

LGTM, thanks for the fix