Remove references to ResourceSet "rancher-resource-set"

[jbiers]

The rancher-resource-set CR will be deprecated as defined in #607. It will be kept temporarily in the v2.11 release to give users the chance to migrate their Backups to use the new definitions. This issue tracks the work to be done for complete removal of the rancher-resource-set for the v2.12 release.

• Remove references to it in Docs.
• Remove it from BRO code.

[omkarkhatavkar]

✅ Tests Executed

🆕 New Rancher 2.12-alpha12

1. User should not be able to create the backup using the deprecated rancher-resource-set – Passed
   

2. User should not be able to see the rancher-resource-set in backup and restore – Passed
   

3. The new rancher-resource-set-full and rancher-resource-set-basic should work as expected and no regression – Passed

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🔼 Upgraded Rancher from 2.11 to 2.12-alpha12

1. rancher-resource-set should not be deleted if it is used in 2.11 – Passed
   

2. Existing backups or recurring backups using rancher-resource-set should work as expected – Passed
   

3. New rancher-resource-set-basic and rancher-resource-set-full should be present and working as expected – Passed
   

4. No Regression – Passed