Generate actions when building the module graph.

This is necessary because GenerateAndroidBuildActions() is effectively a
mutator and therefore can change the data stored in each module.
Sometimes one wants to dump that data in the JSON module graph, and in
order to do so, actions need to be generated.

I briefly entertained removing StopBeforePrepareBuildActions(), but it
incurs a 10-second penalty on "m soong_docs" and "m bp2build" so I
decided to keep it.

Test: Presubmits.
Change-Id: I438aaf981e989dc39a09e8a2ba73f7a08ee55386