L2 constructs for CodeArtifact

## Description

Create L2 constructs for CodeArtifact. Currently only the autogenerated Cfn Constructs are exposed, making work on CodeArtifact repositories and domains tedious.

Here are a few existing issues that have touched on these:
https://github.com/aws/aws-cdk/issues/11131 (open)
https://github.com/aws/aws-cdk/issues/11090 (stalled, closed)

I've taken the code branch from issue 11090 and gotten it working with aws-cdk-lib at https://github.com/alternatejay/aws-cdk/tree/contrib/codeartifact-l2 as a starting point, so it would great to see what is workable here. I'll be linking this issue in the other threads for visibility as well.

## Roles

| Role | User
|---------------------|------------------------------
| Proposed by | @alternatejay
| Author(s) | @alternatejay
| API Bar Raiser | @alias
| Stakeholders | @alias, @alias, @alias

> See [RFC Process](https://github.com/aws/aws-cdk-rfcs#rfc-process) for details

## Workflow

- [x] Tracking issue created (label: `status/proposed`)
- [ ] API bar raiser assigned (ping us at [#aws-cdk-rfcs](https://cdk-dev.slack.com/archives/C025ZFGMUCD) if needed)
- [ ] Kick off meeting
- [ ] RFC pull request submitted (label: `status/review`)
- [ ] Community reach out (via Slack and/or Twitter)
- [ ] API signed-off (label `status/api-approved` applied to pull request)
- [ ] Final comments period (label: `status/final-comments-period`)
- [ ] Approved and merged (label: `status/approved`)
- [ ] Execution plan submitted (label: `status/planning`)
- [ ] Plan approved and merged (label: `status/implementing`)
- [ ] Implementation complete (label: `status/done`)

---

> Author is responsible to progress the RFC according to this checklist, and
apply the relevant labels to this issue so that the RFC table in README gets
updated.

Start by reviewing the related issues 11131 and 11090, then inspect the contrib/codeartifact-l2 branch linked in the description. Follow the RFC checklist in this issue, beginning with API-bar-raiser coordination and an RFC pull request. Done means the API is approved and the RFC progresses through implementation to completion.

Written by the indexing model from the issue text.