Add --processes to list running Maven builds.

[arturobernalg]

Implements a per-user registry under ~/.m2/.maven/runs (create on start, remove on exit). Pure Java 17 using ProcessHandle; no jps or vendor tools.

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Fixes https://github.com/apache/maven/issues/10627

[gnodet]

I think we're missing a mvnsh integration. This can be done by adding a command to the builtin command registry: https://github.com/apache/maven/blob/bcf98382a62f2445a3c65fec5a9c680424414e18/impl/maven-cli/src/main/java/org/apache/maven/cling/invoker/mvnsh/builtin/BuiltinShellCommandRegistryFactory.java#L94

[arturobernalg]

I think we're missing a mvnsh integration. This can be done by adding a command to the builtin command registry:

https://github.com/apache/maven/blob/bcf98382a62f2445a3c65fec5a9c680424414e18/impl/maven-cli/src/main/java/org/apache/maven/cling/invoker/mvnsh/builtin/BuiltinShellCommandRegistryFactory.java#L94

please do another passs