feat!: add schema in Helm for run coordinator
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.
Reviewers: johann, sidkmenon
Reviewed By: johann
Differential Revision: https://dagster.phacility.com/D8737