[EuiFormRow] Allow isDisabled to remove interaction from label

[cchaos]

To elaborate the issue, here is a codepen of the above code with each variation.
(The "dont have permission to fetch" variation made no sense as I wouldn't've displayed the row at all, but I realised I forgot to add the "don't have permission to edit" variation).

I love the UX of labels focusing their inputs, but it doesn't make sense to any scenario other than enabled.

The existing PR was correct in that disabled form row's should disable their inputs (this is not my goal but is definitely relevant and is not a breaking change as disabled doesnt currently exist for form row) but it should also make the label appear like regular text.

And just to clarify & backtrack on my statement in the issue

If the label is disabled then it'd just render a normal EuiFormLabel, with no for attribute

The for attribute should still be present, but we should simply change the appearance to mimic a label without a for i.e., set cursor: default

Originally posted by @j-m in #4899 (comment)

[babs20]

I can go ahead and create a pull request for this issue. I originally did something similar to this in #4908, but removed it due to it not being relevant to the original PR's purpose.

[babs20]

Would this only be for EuiFormRow, or are there other form components that need this functionality as well?

[cchaos]

Well the EuiFormLabel is going to need to accept an isDisabled prop now so that EuiFormRow can just pass it through. But those are the only two that would need to be touched to satisfy this PR.

[babs20]

Sounds good, that was approach I was going to implement.