Remove the option to disable certain components of RCE

[KTrain5169]

Since the introduction of validators, cancel events, experimental schemas and soon preview effects, there are a wide variety of different ways to validate certain conditions before runtime handler, but for most of them, the ability to just disable them causes some "unnecessary" conditional checks to still be required at runtime. Most people will leave them on anyways since it ensures actions will actually work when Neuro/the agent expects it to, so what's the point in keeping them togglable?

I propose that:

• Cancel events are always enabled with the option to disable them deprecated.
• Experimental schemas be removed entirely (see Remove "experimental schemas" #204)
• Remove all redundant code checks for this (caused by cancel events)

For the upcoming preview effects, maybe it could be disabled if the user wishes? It's just a visual effect so it's not important enough to warrant removing its toggle, but also it allows the user to more easily visualise and in the promptGenerator, we can add links conditionally based on the preview effect so that the user can (for example) click a command in the prompt generator box to be taken to the location of the preview effect in the file, or give hints to the user to "look to the file list".