Lambda Layer support

## Problem

we love the Lambda download/upload feature (filter and pagination are very needed)

## Expected behavior

we want the same functionality for layers, download a version/publish the new version

The Toolkit is great Thanks for this 🥇

The issue names the existing Lambda download/upload feature as the reference point but does not identify files or tests. Start by tracing that feature in the toolkit, then determine how Lambda layer versions should be downloaded and published. Done means layer versions support equivalent download and upload behavior, including the requested version handling.

Written by the indexing model from the issue text.