Add support to require Select or Other fields dynamically

Added a patch to resolve this issue.

In summary this adds two parts to add validation:

1. The signature of ElementBase::prepareState() has been updated to accept an array of $states instead of a single string:

- This ensures that callers of this method can now provide not just the visible state, but visible,required states if the field is required.
- This causes the Other text element to be required via JS validation whenever its visible AND required.

2. A new #element_validate callback has been added ElementBase::validateOther()

- This ensures that if JS Validation is disabled (or somehow bypassed) that the validation will be performed server-side.

I have manually tested this on:

- Single-value select lists
- Single-value buttons (radios)
- Multi-value buttons (checkboxes)

With all of the above testing with JS Validation enabled/disabled.

One caveat is if JS Validation is disabled, the logic in ElementBase::validateOther() does not work for Radios. This is related to and caused by the issue that #3171843 🐛 Multiple-value checkboxes do not render existing values Active is trying to fix and its #6 patch will resolve this. (Radios will still successfully work with the JS Validation with/without #3171843 being resolved)

This is the same patch file as above, but can be applied to version 4.0.0

The last submitted patch, 2: add_support_to_require-3356113-2.patch, failed testing. View results →

Added a new patch which removes the changes to ElementBase::prepareState().

While this helped resolve the issues with the logic in ElementBase::validateOther() for Radios, it ended up complicating things when the fields as a whole are required via states by outside logic.

Removing the modified states code also prevents the need to update relevant tests.

Since the issue with ElementBase::validateOther() for Radios is caused by the issue that #3171843 is trying to fix, it should be considered to be a requirement for this task to be completed.