[Enhancement Request] System Schema creation for normal users

As outlined in partition#69 (closed), we need the capability to create system schemas.

Currently system schemas can be only created by service principals. In order to do this the challenge is the authentication, users exists in a partition and system is generic. So for this to work end to end, we need System level users, System level APIs in each service.

This is a high cost solution so, for now as a Phase 1 solution, we're simply creating a bare 'system' partition and provisioning the users in that 'system' partition.

And for this to work end to end:

1. From Schema Service, we're silently passing the data-partition-id as 'system' to entitlements service for Authentication purpose.
2. From Partition Service we're disabling the listing and deletion of this system partition

Once the Phase 2, end to end solution encompassing the complete data platform is done, we can remove the code added in phase 1.