Convert apex transition tag to dependency on apex

When the apex mutator moves to using an info struct instead of a simple
string it becomes difficult to add a dependency directly on the apex
variation of a module, as that would require constructing a matching
ApexInfo to locate it.  Simplify adding the dependency by adding it
on the apex instead, and then traversing from the apex to the desired
module inside the apex.

This causes a few changes in behaviors that require updating tests to
match.

When AlwaysUsePrebuiltSdks is set, the previous behavior was to use
the fragment and its dependencies from the source module for the
platform bootclasspath.  Since the fragment is now found by traversing
from the apex, and the prebuilt apex is preferred, the fragment from
the prebuilt will now be found instead.

prebuilt_bootclasspath lists fragments in apexes that it depends on.
Previously it would depend on the apex variant of the fragment, which
then allowed the fragment to be replaced by the variant from an
override apex that set apex_name.  Now it always depends on the original
apex to find the fragment.

Test: go test ./...
Bug: 372543712
Change-Id: I1a92ff461d4706cf68a0b8b37e53dea412efb8bf

0 files changed, 0 insertions, 0 deletions