This commit updates the Bullseye and Buster containers to pull from a
Google-managed Debian image.

Context:

Google maintains base images for building its own applications. These
images are built from the same source that Docker Hub uses. Therefore,
they match the images you would get from Docker Hub.

The advantage of using Google-maintained images is that they are stored
on Google Cloud, so you can pull these images directly from your
environment without having to traverse networks.

Google updates these images whenever a new version of an official image
is released and the new version fixes a known vulnerability reported by
Artifact Analysis. For more information on image versions, see the
GitHub repository of official images.

See https://cloud.google.com/software-supply-chain-security/docs/base-images

Add a Working with Docker and the Proxy section that explains how to use
the proxy via Docker on a local machine, including some comments about
permissions over the credentials file.

Fixes #2138

When clients run the Proxy in environments where the CPU may be
throttled, the background connection info refresh operation can fail to
complete, causing connection errors. This commit introduces an option
for a lazy refresh. Connection info is retrieved on an as needed-basis
and cached based on the associated certificate's expiration. No
background goroutine runs, unlike the default refresh ahead cache.

 Enable it like so:

 ./cloud-sql-proxy <INSTANCE_CONNECTION_NAME> --lazy-refresh

A lazy refresh may result in increased latency (more requests will be
subject to waiting for the refresh to complete), but gains in
reliability.

Fixes #2183

#2185)

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>