Closes#62758.
Include the Stack log4j config in the Docker image, in order to
make it possible to write logs in a container environment in the
same way as for an archive or package deployment. This is useful
in situations where the user is bind-mounting the logs directory
and has their own arrangements for log shipping.
To use stack logging, set the environment variable `ES_LOG_STYLE`
to `file`. It can also be set to `console`, which is the same as
not specifying it at all.
The Docker logging config is now auto-generated at image build time,
by running the default config through a transformer program when
preparing the distribution in an image builder step.
Also, in the docker distribution `build.gradle`, I changed a helper
closure into a class with a static method in order to fix an
issue where the Docker image was always being rebuilt, even when
there were no changes.
68b5465575