Add ability to provide an authentication session to lock

[yorinasub17]

Description

This PR updates the lock library to support using an already configured/authd AWS session. The use case for this is in the refarch-deployer utility, where all the authentication is handled internally based on where you are running, and more specifically, the local case where we use aws-vault as a library to auth to the different accounts, so the default credential chain is empty.

TODOs

Please ensure all of these TODOs are completed before asking for a review.

• [x] Ensure the branch is named correctly with the issue number. e.g: feature/new-vpc-endpoints-955 or bug/missing-count-param-434.
• [x] Update the docs.
• [x] Keep the changes backward compatible where possible.
• [x] Run the pre-commit checks successfully.
• [x] Run the relevant tests successfully.

[yorinasub17]

Thanks for review! Merging now.