java-openliberty: cache maven dependencies in stack image for codewind + (no-mount scenarios)

[scottkurz]

The command-line appsody user will use the mounts defined in the stack image APPSODY_MOUNTS envvar, mounting to the host ~/.m2.

However codewind's appsody integratoin doesn't use these mounts.

To the CLI user, it doesn't make too much sense to aggressively cache, inside the stack image, the maven dependencies the stack will likely use, since the host .m2 will be bind mounted over this anyway.

However, for codewind we would benefit from doing something like we do in appsody build with the preload-m2-pom.xml file.

Or we might ultimately decide not to, not to make the image any bigger...but worth looking into.

[neeraj-laad]

Another issue and PR that relates to this is appsody/appsody#895

[scottkurz]

A challenge here is that the stack encompasses apps starting from all templates (and non-template apps)... so a cache highly-focuses on say default template could add unused bloat for another template.