Provide project-relative maven installation

[tivervac]

As discussed (see below and here), it would be useful to be able to configure the default maven installation to run maven launch configs. This would simplify team management and facilitate reproducible dev environments and reproducible builds over Tycho and Eclipse through m2e.

This can be done by

• allowing Eclipse variables (such as $WORKSPACE_LOC and $PROJECT_LOC) to configure the m2e maven installations
• allowing to set a default maven installation for running maven launch configs

In the end, the solution I see is to be able to use the project-locally-installed mvnw. Any other alternative to the above that achieves the same result is greatly appreciated.

Discussed in #1335

^{Originally posted by tivervac March 27, 2023}
When I explore my installations, I see that it mentions I have no WORKSPACE installation available

This entry is not editable. If I try to add a new installation, I'm only given the option for External installations, which doesn't seem to allow relative path or the external tool variables.

How can I add a workspace maven installation? Is it supposed to be provided by a plugin?

[tivervac]

Created an actual feature proposal such that it can potentially be picked up in the Eclipse IDE WG's Prioritized Dev Effort #4. For this ticket to be accepted under that issue, please assign the usability label.

\cc @jonahgraham