Add support for Customer Managed Keys (CMK) for CodeBuild access

Many organizations limit S3:PutObject operations on S3 buckets without customer managed keys (CMKs). During the invoke ( ) call, a CodeBuild project is created behind the scenes which stores source files and artifacts in S3, and CodeBuild is blocked by the mentioned SCP.

Please instrument the starter-toolkit to support optional passing of CMK ARN into the configure( ) call

Start by reading the configure() implementation and the invoke() path that creates the CodeBuild project and stores source files or artifacts in S3. Trace how an optional CMK ARN could flow through configure() to the CodeBuild-related operations; done means callers can provide the ARN while existing calls continue to work.

Written by the indexing model from the issue text.