Associate FormControl.Validation with the relevant input

[joshfarrant]

Summary

Adds the FormControl.Validation component's id to the FormControl input's aria-describedby to help assistive tech understand the relationship between the input and the validation message.

List of notable changes:

• Adds aria-describedby to FormControl input for FormControl.Validation component
• Adds tests for FormControl.Validation association with the input
• Adds missing tests for FormControl.Hint association with the input

What should reviewers focus on?

• Check that you can see the aria-describedby association in the HTML
• Bonus points for testing with a screen reader

Supporting resources (related issues, external links, etc):

• Closes https://github.com/github/primer/issues/3780

Contributor checklist:

• All new and existing CI checks pass
• Tests prove that the feature works and covers both happy and unhappy paths
• Any drop in coverage, breaking changes or regressions have been documented above
• UI Changes contain new visual snapshots (generated by adding update snapshots label to the PR)
• All developer debugging and non-functional logging has been removed
• Related issues have been referenced in the PR description

Reviewer checklist:

• Check that pull request and proposed changes adhere to our contribution guidelines and code of conduct
• Check that tests prove the feature works and covers both happy and unhappy paths
• Check that there aren't other open Pull Requests for the same update/change

Screenshots:

Please try to provide before and after screenshots or videos

Before	After

[changeset-bot]

🦋 Changeset detected

Latest commit: f3303c0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@primer/react-brand	Patch
@primer/brand-primitives	Patch
@primer/brand-e2e	Patch
@primer/brand-fonts	Patch
@primer/brand-config	Patch
@primer/brand-storybook	Patch

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[github-actions]

🟢 No design token changes found

[github-actions]

🟢 No visual differences found

Our visual comparison tests did not find any differences in the UI.