(aws-cdk/aws-amplify): Add a sourceCodeProvider for bitbucket. Currently only supports GitLab, GitHub and CodeCommit

I am trying to setup a cdk pipeline to deploy a react app on AWS Amplify. Although, I am unable to use bitbucket as a source code provider.

### Use Case

Setting up a new project on amplify through bitbucket is possible using the AWS console. But cdk doesn't have support for this.

Currently, as a workaround, I had to revert back to using CodePipeline and S3 bucket to deploy my react app through cdk, which isn't ideal.

### Proposed Solution

Create a new source code provider for bitbucket like the one that already exists for Github, Gitlab and CodeCommit - https://docs.aws.amazon.com/cdk/api/latest/docs/@aws-cdk_aws-amplify.GitHubSourceCodeProvider.html

* [ ] :wave: I may be able to implement this feature request
* [ ] :warning: This feature might incur a breaking change

---

This is a :rocket: Feature Request

Start by comparing the existing GitHub, GitLab, and CodeCommit source-code providers in the AWS CDK Amplify implementation, using the GitHubSourceCodeProvider API documentation linked in the issue. Confirm the AWS Amplify Bitbucket provider requirements, then add equivalent CDK support and verify that a React app can use Bitbucket as its source instead of the stated CodePipeline and S3 workaround.

Written by the indexing model from the issue text.