updates layer to also use layername:version

[ykethan]

Problem

Issue number, if available:

Changes

We can currently use an ARN to add a layer. This PR would add support for just providing the layerName:version where the account-id and region are auto inferred using cdk improving DX.

example:

   layers: {
   "sharp": "SharpLayerGen2:1", 
   "@aws-lambda-powertools/logger":
      "arn:aws:lambda:us-east-1:094274105915:layer:AWSLambdaPowertoolsTypeScriptV2:12",
    },

Corresponding docs PR, if applicable:

Validation

Checklist

• If this PR includes a functional change to the runtime behavior of the code, I have added or updated automated test coverage for this change.
• If this PR requires a change to the Project Architecture README, I have included that update in this PR.
• If this PR requires a docs update, I have linked to that docs PR above.
• If this PR modifies E2E tests, makes changes to resource provisioning, or makes SDK calls, I have run the PR checks with the run-e2e label set.

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

[changeset-bot]

🦋 Changeset detected

Latest commit: b4b3e9d

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

This PR includes changesets to release 2 packages

Name	Type
@aws-amplify/backend-function	Minor
@aws-amplify/backend	Minor

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[Amplifiyer]

Looks good.

[rtpascual]

Nice!