Support fully qualified names in `android:"path"` properties

Previously, a module reference in a path property would be parsed into
two parts, the module name and the optional output tag, which defaults
to an empty string if not specified. The output tag would be stored in
a sourceOrOutputDependencyTag which would then be used, along with the
module name to add a dependency on the module.

Later, when the paths were processed the same module reference would be
parsed into the same two parts again and the module name used to find a
matching Module by comparing it against the name returned by either
Module.Name(), ctx.OtherModuleName() or ModuleBase.BaseModuleName().
Once the module had been found then if it supported OutputFilesProducer
then the tag would be passed to its OutputFiles(tag) method. Otherwise,
it would fall back to treating it as SourceFilesProducer.

The problem with that is the module name retrieved from the module in
some way (either directly or through a context name) could be different
to that originally supplied when adding the dependency. e.g.
1. If the original dependency was added onto a source module but there
   existed a suitable and preferred prebuilt module then the dependency
   onto the source module would have been replaced by the prebuilt
   module which has a different name.
2. If the path property included a fully qualified name that included
   a qualifying path then it would not match the name retrieved from
   the module which would not include the qualifying path.

This change circumvents that whole issue by adding the module name that
was originally used to add the dependency into the DependencyTag. Now
the DependencyTag uniquely identifies the original module/outputTag
pair parsed from the module reference. The pathDepsMutator guarantees
that they are unique as it dedups them before adding the dependencies.

It is possible that calling ExtractSource(s)Deps() would add some
duplicate but if they did they would be identical, i.e. the same
sourceOrOutputDependencyTag would be used to add a dependency onto the
exact same module. In that case it would not matter which of the
dependencies was found as it would still return the same module.

Bug: 193228441
Test: m nothing
Change-Id: I661514a2984818e5c26577411cede53eb57bcd02