CXX-3265 Update release instructions to use Amazon ECR instead of Artifactory

[eramongodb]

Resolves CXX-3265. Applies changes similar to those in mongodb/mongo-c-driver#2058.

• Release instructions are updated to authenticate with and use Amazon ECR instead of Artifactory.
• Dockerfiles under extras/docker are updated to support setting a DEFAULT_SEARCH_REGISTRY environment variable (pass to make) which is forwarded as a Docker default_search_registry argument, similar to default_search_registry for the Earthfile in CDRIVER-5971 Use Amazon ECR to obtain OCI images in EVG mongo-c-driver#2058. (Note: Earthfile syntax slightly differs from Dockerfile syntax.)

The generate.py script and related files has been drive-by improved for better consistency (e.g. trailing newlines) and with inline script metadata to support uv run.

[kevinAlbs]

LGTM with minor comments.

[kevinAlbs]

Remove stray RUN true?

[kevinAlbs]

Suggested change

	"alpine3.19": "\nRUN true",
	"alpine3.19": "",

Remove unnecessary RUN true? I expect these changes were for newline consistency. Since a newline is later appended, I expect this can be empty.

[eramongodb]

Annoyingly, if the expansion is empty (prior value of ""), the Dockerfile for alpine3.19 ends up with a trailing newline:

  COPY --from=builder /opt/mongocxx /usr/local
+ (empty line)
  (EOF newline)

I could not find a way to coerce Jinja2 to avoid expanding {{ post_install_commands }} without an extra newline given a value of "" or None. For typical Jinja2 expansions, one would use % (e.g. {% var %}), but that doesn't seem to apply to {{ var }} expansions... 😕

[kevinAlbs]

No longer used:

Suggested change

	: "${ARTIFACTORY_USER:?}"
	: "${ARTIFACTORY_PASSWORD:?}"

[kevinAlbs]

No longer used:

Suggested change

	'ARTIFACTORY_PASSWORD',
	'ARTIFACTORY_USER',