This reduces the copy/paste of validation code. Constraint validation must be synchronous, so a `Validator` helps compute the validity and cache it since the validity must be checked when properties change.
Implemented in checkbox-like controls.
PiperOrigin-RevId: 584380464
Part of adding constraint validation mixins. Each component that participates in constraint validation has different rules and error messages for validating. The `Validator` gives `mixinConstraintValidation()` a way to compute and cache validation.
Other validators will be added later, such as `SelectValidator` and `RadioValidator`
PiperOrigin-RevId: 583508468
BREAKING CHANGE: Rename `@material/web/<component>/lib` to `@material/web/<component>/internal`. Prefer not using internal files.
PiperOrigin-RevId: 550633216