Add Frontend Validations for Seat Controls User Cap Option

What does this MR do and why?

Add frontend validations for seat controls user cap option

Disable user cap input when seat controls is set to off Require user cap input when seat controls is set to user cap

This is based on !161747 (closed), specifically this commit: !161747 (38eede4a)

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/477091

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Screen recordings

Before	After
FrontendValidationsBefore-small	FrontendValidationsCorrect-small