bootclasspath_fragment must only depend on source contents

This change ensures that bootclasspath_fragment only depends on source
modules and prebuilt_bootclasspath_fragment only depends on prebuilt
modules.

It does that in two ways:
1. It adds the dependencies in ComponentDepsMutator method which is
   called before any renaming of prebuilts is done which makes it very
   easy to add a dependency directly onto either the source or prebuilt
   as required.
2. It uses a tag which prevents dependencies on a source module from
   being replaced with a dependency on a prebuilt module which ensures
   that a dependency on the source modules is not replaced with a
   dependency on a prebuilt module.

Bug: 177892522
Test: m nothing
Change-Id: Ibcfae39083afbc07fcf729ead3ed5f5d020845bf