Add aws_account_region resource

[turkenf]

Description of your changes

This PR adds the Region.account.aws.upbound.io/v1beta1 resource to enable or disable a particular region for an AWS account.

Fixes #1137

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable to ensure this PR is ready for review.
• Added backport release-x.y labels to auto-backport this PR if necessary.

How has this code been tested

Manually tested

• After applying the YAML with regionName: ap-southeast-3 and enabled: true

• After the resource is successfully created:

status:
  atProvider:
    accountId: ""
    enabled: true
    id: ap-southeast-3
    optStatus: ENABLED
    regionName: ap-southeast-3
  conditions:
  - lastTransitionTime: "2024-09-18T19:46:01Z"
    reason: ReconcileSuccess
    status: "True"
    type: Synced
  - lastTransitionTime: "2024-09-18T19:57:37Z"
    reason: Success
    status: "True"
    type: LastAsyncOperation
  - lastTransitionTime: "2024-09-18T19:57:38Z"
    reason: Available
    status: "True"
    type: Ready
  - lastTransitionTime: "2024-09-18T20:02:03Z"
    reason: UpToDate
    status: "True"
    type: Test

• Removing the resource from the cluster means that the provider will stop managing of this region, which will have no effect. To disable the region, must be set enabled: false.

[mergenci]

Thanks @turkenf. LGTM.