Make it hard to accidentally enable an experimental feature flag (backport #11998) (backport #12058)

[mergify]

Currently it's easy to enable an experimental feature flag like khepri_db by accident. Given the operation is irreversible, this leads to serious consequences when done in a production environment.

This PR implements the following changes:

• Management UI
  • Split the feature flags page into two tables - first with all but experimental feature flags, the second with only the experimental flags (and a warning)
  • To enable an experimental feature flag, a checkbox needs to be toggled first
• CLI
  • rabbitmqctl enable_feature_flag khepri_db won't work unless a new flag --experimental is provided

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This is an automatic backport of pull request #11998 done by [Mergify](https://mergify.com).

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This is an automatic backport of pull request #12058 done by [Mergify](https://mergify.com).

[dmitrynovik]

Thanks @mkuratczyk
I think the --force flag is a very good idea!

I'm not so convinced about the UI.
Maybe it's good not to list experimental features in UI at all to avoid the temptation?

[michaelklishin]

@dmitrynovik they are now listed in a separate category and require an explicit confirmation. The idea is certainly not to hide experimental feature flags. We've had a grand total of 1 up to this point, and in 4.0, that feature flag graduates to be a regular one.

[dmitrynovik]

Also, semantically --include-experimental would probably be a better name than --force.

P.S. Looking in the changed files, seems like it's --experimental :)

[mkuratczyk]

I forgot to update the PR description but the flag was changed during the PR review process and what we merged, actually uses --experimental rather than --force. For additional safety --experimental is rejected if the feature flag is all - experimental features need to be explicitly specified to be enabled from the CLI