Added support for Linux package codesigning

[ellbosch]

Note: these changes have already been validated with Azure DevOps with successful runs.

This PR updates our Dockerfile scripts for debian and rpm packaging in the following ways:

• Adds support for codesigning. Dockerfiles have new commands to copy deb and rpm packages to the root of the container, which enables Docker to copy packages from the container to the host. With packages now in the host, we can run the ESRP DevOps codesign task.
• Removes Python dependency installation in Dockerfile. DevOps pipelines have been updated to publish packages directly from the host, rather than from Docker. With this change, there's no longer a dependency on our Python code to publish deb and rpm packages to daily storage.
• Updated docs. Release docs have now been updated to reflect the aforementioned changes to publishing. I've also added the sh suffix to codeblocks for formatting.

[pensivebrian]

So we're hardcoding and assuming a /Repos/mssql-cli? Seems fine for docker, but we can't make this assumption for dev boxes.

[ellbosch]

For sure, I've accounted for this.