Support for refreshing bsp projects on BUILD file change

[lukaszwawrzyk]

There is already a file watcher that creates a popup notification with link to project refresh when BUILD file changes.
This PR updates the method that the hyperlink points to - PantsUtil.refreshAllProjects, so that in case of project imported from bsp rather than from pants, it would also refresh the project correctly.

Also the change in findBuildRoot was needed (look for pants root in module content roots if it was not found from .iml file) as otherwise the root module could not be found given layout generated by fastpass. Because of that the file watcher was never setup.

[olafurpg]

This is great! Thank you @lukaszwawrzyk for looking into this.

I'm wondering if we could somehow add a basic integration test that imports a Pants build via BSP? The "fastpass" command-line tool can be launched via coursier using a command like

./coursier launch \
  org.scalameta:metals_2.12:0.8.0+305-60af6828-SNAPSHOT \
  -r sonatype:snapshots \
  --main scala.meta.internal.pantsbuild.BloopPants -- \
  create --name refresh-projects --intellij src::

It's OK to skip it if you consider it's too much effort. We can open a separate ticket to track progress on adding BSP integration tests.

[wisechengyi]

Thanks, @lukaszwawrzyk !