Support java.import.maven.projectNameTemplate per workspace folder #4568

Follow-up to #4552.

In a multi-root workspace, java.import.maven.projectNameTemplate can only be set in User or Workspace settings, so all folders share one template. It would be useful to set a different template per folder.

Requested by @FlyingSheepOnSailfish in eclipse-jdtls/eclipse.jdt.ls#3948