Update Scheduler helm schema to use enum types

Summary:
Depends on D5748

As the title, enumify the helm scheduler values, rather
than relying on a boolean toggle.

Test Plan:
bk/helm lint
integration

Reviewers: nate, catherinewu, alangenfeld

Reviewed By: alangenfeld

Differential Revision: https://dagster.phacility.com/D4920