Duplicate test running information in `tox.ini` and CI workflows

[ocelotl]

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We have duplicate information about the tests we run in CI and in tox.ini.

For example, tox.ini specifies that a particular package is to be run using certain python versions:

    ; opentelemetry-instrumentation-asyncpg
    py3{8,9,10,11,12}-test-instrumentation-asyncpg
    ; ext-asyncpg intentionally excluded from pypy3
    lint-instrumentation-asyncpg

The equivalent information (not running this package with pypy) is stored in the Github workflow file:

        exclude:
          ...
          - python-version: pypy3
            package: "asyncpg"

There is nothing that guarantees these 2 sources of information match. This can lead to packages failing and not being detected in CI because they are not being run in CI at all, or to having python versions specified in tox.ini for a certain package that actually don't work but we don't realize that because we have excluded them in our workflow files.