connectors-ci: use the new connectors-ci command to run connector nightly builds

[alafanechere]

When the connectors-ci pipeline will be able to test and build all our connectors we shall use it to power our nightly builds.

We should be able to have the tests/builds for GA, Beta, and alpha connectors run in the same GHA as we'll benefit from the beefy runner pool the infra team will provide. This runner pool will have docker and pip caches that should make the nightly build faster than today.

The two following workflows should be replaced by a single one calling connectors-ci --is-ci test-connectors (all our connectors will be tested by default with this command).

• https://github.com/airbytehq/airbyte/blob/master/.github/workflows/connector_integration_tests_alpha.yml
• https://github.com/airbytehq/airbyte/blob/master/.github/workflows/connector_integration_tests.yml

Inspiration should be taken from this workflow to run connectors-ci in GHA:
https://github.com/airbytehq/airbyte/blob/master/.github/workflows/connector_integration_tests.yml#L1