feat(codebuild): macOS codebuild support (#31203)

### Issue # (if applicable)

Closes #31170.

### Reason for this change

CodeBuild recently added support for Mac builds.
https://aws.amazon.com/about-aws/whats-new/2024/08/aws-codebuild-mac-builds/

The CDK can to be extended to support Mac CodeBuild fleets, as well as
using those fleets in CodeBuild projects.

### Description of changes

- Added `MAC_ARM` value to EnvironmentType
[enum](https://github.com/aws/aws-cdk/blob/main/packages/aws-cdk-lib/aws-codebuild/lib/environment-type.ts)
- Added `MacBuildImage` to
[project.ts](https://github.com/aws/aws-cdk/blob/main/packages/aws-cdk-lib/aws-codebuild/lib/project.ts)

All design decisions were made by following the previous precedent set
by `LinuxBuildImage` and `WindowsBuildImage`.

### Description of how you validated changes

I added unit tests and integration tests for `MacBuildImage`. I ensured
that the CDK was able to build, and that the output CloudFormation stack
had the correct resources. I also successfully built the Codebuild
project that was deployed.

### Checklist
- [X] My code adheres to the [CONTRIBUTING
GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and
[DESIGN
GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

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*By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache-2.0 license*

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Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>