protectedts: switch backup, changefeed tests to use the new protected timestamp subsystem

[arulajmani]

Describe the problem

Now that everything laid out in #73727 has landed, we have an end to end implementation for the new protected timestamp subsystem. This should allow us to switch over existing tests to leverage the new subsystem instead of the old one. This entails flipping:

cockroach/pkg/kv/kvserver/protectedts/testing_knobs.go

Lines 18 to 24 in 6ea1c5e

	// EnableProtectedTimestampForMultiTenant when set to true, runs the protected
	// timestamp subsystem that depends on span configuration reconciliation.
	//
	// TODO(adityamaru,arulajmani): Default this to true, or flip it to
	// `DisableProtectedTimestampForMultiTenant` prior to release 22.1.
	EnableProtectedTimestampForMultiTenant bool
	}

and fixing whatever the falls out as a result.

Jira issue: CRDB-13621

[adityamaru]

Fixed by #77478

[blathers-crl]

cc @cockroachdb/bulk-io