[BUG] Add serviceAccountName override for Ray

[peterghaddad]

Describe the bug

Currently, the serviceAccount pulls from the securityContext of the k8s cluster that the FlytePropeller is deployed at. Instead, have the option to configure the propeller to use a specific serviceAccountName on k8s.

Expected behavior

When the SA is set to something other than the default value, then pull the serviceAccountName from the propeller config

Additional context to reproduce

No response

Screenshots

No response

Are you sure this issue hasn't been raised already?

• [X] Yes

Have you read the Code of Conduct?

• [X] Yes

[peterghaddad]

related to #4920

[Sovietaced]

I believe this has been fixed.