Add DB-API sqlcomment mysql_client_version fallback

[tammy-baylis-swi]

Description

Stops stacktraces when programmatic instrumentation with sqlcommenting is enabled in some cases.

Fixes #3730

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 unit tests
• Applied local change to manual instrumentation similar to Add sqlcommenter example to docs opentelemetry-python#4734

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

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

[xrmx]

Please add some docker tests, I fixed a crash in the psycopg commenter code extracting the libpq version recently and the mocks were not matching reality.

[tammy-baylis-swi]

Please add some docker tests, I fixed a crash in the psycopg commenter code extracting the libpq version recently and the mocks were not matching reality.

@xrmx done, ptal.

I tried to add one for the unknown fallback in couple ways that won't work. Attempting a patch in docker-tests results in AttributeError: '_mysql_connector.MySQL' object attribute 'get_client_info' is read-only. Similarly, can't remove _cmysql from mysql.connector at test time. Unit test coverage is adequate I hope.