feat!: add schema in Helm for run coordinator

Summary:
Previously, the run coordinator was allowed a custom class, but its configuration did not
fit the convention of "type:, config:" since that would be a breaking change. Here, we migrate
the schema to this convention.

Will change queuedRunCoordinator to runCoordinator in a followup.

Test Plan:
pytest
integration

Reviewers: johann, sidkmenon

Reviewed By: johann

Differential Revision: https://dagster.phacility.com/D8737