This patch adds support for custom IDs in the `TextControl` component.

Currently any passed ID prop is ignored, and a auto-generated value is
used instead.

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Resolves WordPress#24749

Changing the test setup for labels to be more `testing-library` idiomatic.

Adding line item under Enhancements to include `TextControl` changes.

…s_contains_an_id

Dropping the old `useUniqueId` pattern in favour of the more succinct and complete `useInstanceId` usage.