ci-connector-ops: enforce connector metadata checks on connector PR

[alafanechere]

Tell us about the problem you're trying to solve

@evantahler recently accomplished huge grooming chores of our connector's documentation:
#20274
#19865
#20666

We don't want to perform this cleaning anymore and would like to enforce clean docs / connector metadata before they merge into the master branch.

Describe the solution you’d like

When a connector version is bumped in a PR we should check that:

• A documentation file is available for this connector in docs/integrations/*
• The changelog was correctly updated
• The connector image was published to our docker registry (this is already done by the Ensure Image exists check)
• A valid version number is used?
• Enforce the presence of a valid connector icon? (already tracked in Connector Ops CI Checks enforces that Beta+ connectors include an icon #19448)

Benefits:

• CAT team and members of the maintainer program will benefit from automated checks that can help improve the quality of their PR reviews
• It will help keep a consistent connector catalog with quality artifacts used on Airbyte cloud (connector docs, icon)

Where should this be coded?

We had an interesting discussion here about where this kind of check should happen.
As the connector metadata we are checking are not part of the Airbyte protocol at the moment I think these check should not happen in SAT. I suggest to add the metadata validation logic to ci-connector-ops.
We would ideally have a CLI command targeting a connector folder and performing the check.
We'd run this command from the Connector Ops CI workflow.
We should keep in mind that we plan to enable connector development outside of the monorepo in a near future. It would be nice to make sure that these checks can be performed in this context without huge refacto.

[alafanechere]

Closing as this is part of the QA checks of this project #21709