[AWS] Only create admin SP if SAT is being used

[JDBraun]

Can remove the admin SP from normal workflows, since it isn't complex code to add-on. In addition, since an SP is now enforced for TF, and not basic auth, the user would know how to do so manually in a worst case scenario

[JDBraun]

decided to use the same SP that is being used for the OAuth to keep one ownership across the board

[jdbraun-db]

updated with #94

• we use the same SP that does the account admin for the entire repo, no additional SP is created.

  terraform-databricks-sra/aws/tf/modules/sra/databricks_workspace.tf

  Line 90 in 7bfbcd8

  client_id = var.client_id