Textarea > Update character counter UX and placement

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### Description

Reconsider the placement of the character counter text and reconsider how the information can be more clearly conveyed. The current counter shows one number, but doesn't provide any comparison.

As uncovered in https://gitlab.com/gitlab-org/gitlab-ui/-/merge_requests/2738#note_896569524, the current placement of the counter collides with both text within the textarea and the scrollbar.

### Proposal

- Move the character counter outside of the textarea bounding box.
- Left align the character counter. This follows other form practices where labels and controls are left aligned and help with scanability.
- Use either a text explanation of what's happening with the counter, or two values so that the limit is always visible.
- The character counter is basically help text, so it seems to make sense to treat it as such. Additional help text and any validation messages would be below the character counter.
- Remove text highlight (adds a lot of development complexity).
- Only change the color for text when the count has been exceeded. The blue conflicts with text that is linked.

| **Current** | **Option A with {#}/{#}** | **Option B with text** |
| ------ | ------ | ------ |
| ![image](/uploads/60ce1c2017854ba471fb0035dc0658cb/image.png) | ![image](/uploads/24d0d967ee662bd2ad3c0e1fe2ea63b1/image.png) | ![image](/uploads/5685967d635bcde1e9975bda9ef49221/image.png) |

#### Accessibility considerations

- Visible feedback should also be available/announced for screen reader users. For example, after a pause in typing the limit status is announced via an `aria-live="polite"` region.
- The placement of the counter could be out of view with screen magnification turned on, but form validation should help with any error remediation. 

### Figma file

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[View working file in Figma →](https://www.figma.com/file/qEddyqCrI7kPSBjGmwkZzQ/branch/ubxFCR4pADM7ZfMJ7ZvyOU/Component-library?node-id=49840%3A75722)

### Checklist

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[annotation]: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/blob/main/doc/pajamas-ui-kit.md#adding-descriptions-notes-and-annotations
[building]: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/blob/main/doc/pajamas-ui-kit.md#building-components
[foundations-team]: https://about.gitlab.com/company/team/?department=ecosystem-foundations-team
[figma-maintainer]: https://about.gitlab.com/handbook/engineering/projects/#design.gitlab.com
[publishing]: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/blob/main/doc/pajamas-ui-kit.md#publishing-changes
[structure]: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/blob/main/doc/pajamas-ui-kit.md#structure
[component-guideline-template]: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/blob/main/.gitlab/merge_request_templates/component-guideline.md
[component-archive]: https://www.figma.com/files/project/5472112/Component-archive
[misc-archive]: https://www.figma.com/files/project/10620392/Misc-archive
[gitlab-ui-component-template]: https://gitlab.com/gitlab-org/gitlab-ui/-/issues/new?issuable_template=Component
[issue-component-template]: https://gitlab.com/gitlab-org/gitlab-services/design.gitlab.com/-/issues/new?issuable_template=Component%20documentation

Story points: 1.0