Deprecate oauth2 settings

[MarcialRosales]

Proposed Changes

Implements these 2 features which essentially deprecate two settings:

• Deprecate auth_oauth2.jwks_url and its corresponding erlang config entry  #12239
• Deprecate management.metadata_url and move it to auth_oauth2.discovery_endpoint_path  #12237

This PR adds the new settings while keeping the old ones until 4.2.x when they will be removed.
If the user configures the old and the new setting, RabbitMQ will take the value from the new setting
If the user configures the only the old setting, RabbitMQ uses it.

Types of Changes

What types of changes does your code introduce to this project?
Put an x in the boxes that apply

• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)
• Build system and/or CI

Release note

It should be mentioned in the release notes these two changes and the fact that users currently using auth_oauth2.jwks_url and/or management.oauth_metadata_url they are affected and they should modify their configuration.
Any reference to auth_oauth2.jwks_url should be renamed to auth_oauth2.jwks_uri. Likewise any reference in the legacy schema should be renamed to. i..e key_config.jwks_url to key_config.jwks_uri.
Any reference to management.oauth_metadata_url should be removed and instead configure the auth_oauth2.discovery_endpoint_params accordingly. There is a section in the docs that cover this in detail.

cc @pstack2021