Allow tagged (e.g. encrypted:...) values for more rabbitmq.conf keys (backport #15808) (backport #15810)

[mergify]

When the support for tagged values in rabbitmq.conf was introduced #11989, not all candidate keys were immediately marked as supporting these new value types.

This PR updates a few more sensitive rabbitmq.conf keys to support encrypted:... values.

References #11989, #15807.

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This is an automatic backport of pull request #15808 done by [Mergify](https://mergify.com).

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This is an automatic backport of pull request #15810 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 1c6aee5 has failed:

On branch mergify/bp/v4.2.x/pr-15810
Your branch is ahead of 'origin/v4.2.x' by 1 commit.
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You are currently cherry-picking commit 1c6aee5ae.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
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Changes to be committed:
	modified:   deps/rabbit/priv/schema/rabbit.schema
	modified:   deps/rabbit/test/config_schema_SUITE_data/rabbit.snippets
	modified:   deps/rabbitmq_peer_discovery_etcd/test/config_schema_SUITE_data/rabbitmq_peer_discovery_etcd.snippets
	modified:   deps/rabbitmq_stomp/test/config_schema_SUITE_data/rabbitmq_stomp.snippets

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   deps/rabbitmq_auth_backend_ldap/test/config_schema_SUITE_data/rabbitmq_auth_backend_ldap.snippets

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