API: Add deprecation notice for updating folder UID

[papagian]

What is this feature?

Adds a deprecation notice for updating folder UIDs using the API: PUT /api/folders/:uid

Why do we need this feature?

UIDs as identifiers should be immutable. Related to #60983

Who is this feature for?

[Add information on what kind of user the feature is for.]

Which issue(s) does this PR fix?:

Fixes #

Special notes for your reviewer:

• After merging this we need to update also What's new doc
• the OpenAPI specs contain changes unrelated to this (they seem to be outdated)

Please check that:

• It works as expected from a user's perspective.
• If this is a pre-GA feature, it is behind a feature toggle.
• The docs are updated, and if this is a notable improvement, it's added to our What's New doc.

Deprecation notice

Starting with 10.0, changing the folder UID is deprecated. It will be removed in a future release. Please avoid using it because it can result in folder losing its permissions.

[grafanabot]

Hello @papagian!
Backport pull requests need to be either:

• Pull requests which address bugs,
• Urgent fixes which need product approval, in order to get merged,
• Docs changes.

Please, if the current pull request addresses a bug fix, label it with the type/bug label.
If it already has the product approval, please add the product-approved label. For docs changes, please add the type/docs label.
If the pull request modifies CI behaviour, please add the type/ci label.
If none of the above applies, please consider removing the backport label and target the next major/minor release.
Thanks!