chore(Examples): Customize KMS Client

[texastony]

Issue #, if available: https://github.com/aws/aws-encryption-sdk-java/issues/1985

Description of changes:

• Demonstrate Client Supplier

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

Check any applicable:

• [ ] Were any files moved? Moving files changes their URL, which breaks all hyperlinks to the files.