Add docker-tests coverage of metrics export

[tammy-baylis-swi]

Description

Adds docker-tests coverage of metrics export: general test (did not exist), test focused on max_export_batch_size without mocks, for both gRPC and HTTP. Updates the docker-compose for otelcollector version used.

Extending the MetricExporter classes to count batches is hopefully reasonable. Trying to capture otelcollector debug output then parse exact metrics values for "batches forwarded" is too much, imo.

Fixes #5031

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• Added more to existing opentelemetry-docker-tests

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[anuraaga]

Is it possible to remove the old mock tests in this PR too? Otherwise a quick followup would be great since it blocks #4976

#4976 (comment)