Make airbyte-platform repo build leaner

[cgardens]

What

• The airbyte-platform build currently runs a lot of stuff, arguably for no reason. We need to be more intellectually clear eyed on what we're trying to achieve here. The airbyte-platform build should verify that the code can be built and run unit tests so that an OSS contributor could develop locally. It is not trying to rigorously qualify commits for release (we do that internally).

How

With that vision in mind, this PR does the follow:

• removes the frontend e2e test run -- we do this internally on each commit and when we cut an oss release.
• removes the helm acceptance test run -- this hasn't worked for ever because we never updated the test configuration. we now test this internally and the deployments team is in charge of qualifying oss releases. e wouldn't ask a contributor to run it anyway.
• removes the docker acceptance tests run -- again this is tested internally, not a lot of value in re-running it. we wouldn't ask a contributor to run it anyway.
• moves the platform build to use the default gh runners -- now that all we're doing is effective ./gradlew build we do not need beefy runners for it. while using the stock runners is a little slower (10 minutes instead of 7), because there is no developer iteration loop that depends on this, this is one of the few places where I think we are okay with it being a bit longer.
• the notification action was broken because it was referencing .github/actions/match-github-to-slack-user/action.yml which was only in the internal repo. copied it over.
• remove python from the build -- nothing in the platform uses it.
• remove test coverage -- we do this internally, not adding much here. not a useful feedback loop for a contributor.
• remove "Test if Seed spec is updated" -- there is no action a contributor can take on this to fix it
• skip airbyte-workers-commons:test because the tests use too much memory (doesn't work on gh runners or aws runners), we need to fix this test suite to use a reasonable amount of memory.

Recommended reading order

1. .github/workflows/gradle.yml

Can this PR be safely reverted and rolled back?

• YES 💚
• NO ❌

[CLAassistant]

All committers have signed the CLA.

[cgardens]

/create-oss-pr