Page is part of experiment labels

[mfendeksilverstripe]

Description

It would be a good idea to add some messages to the CMS page edit form of pages which are part of an active experiment. This covers:

• entry pages
• variation pages

For entry pages it highlights to content authors that the page has active redirection via the experiment applies which is something that might not be obvious.

For variation pages it's important to note that these pages must not get unpublished otherwise this might break the active experiment.

Additional context or points of discussion

No response

Validations

• You intend to implement the feature yourself
• You have read the contributing guide
• You strongly believe this feature should be in core, rather than being its own community module
• You have checked for existing issues or pull requests related to this feature (and didn't find any)