Convert rust module-info.json to soong

This leads to idendical results as before, with the exception of
the "required" field in module-info.json. Make has more complicated
logic to fill out the required field than soong, and it leads to
make-specific names such as ones suffixed with :32 and don't make sense
in soong. I'm don't think there are critical users of that field though,
so I'll try removing it.

Everything else should be identical to the make-generated information
though.

Bug: 389720048
Test: diff'd module-info.json before and after this cl in soong+make mode
Change-Id: I74aefe578287f07474c15e5f92a0c2780a679047
diff --git a/rust/source_provider.go b/rust/source_provider.go
index 3236bce..27c62c2 100644
--- a/rust/source_provider.go
+++ b/rust/source_provider.go
@@ -43,6 +43,7 @@
 	SourceProviderProps() []interface{}
 	SourceProviderDeps(ctx DepsContext, deps Deps) Deps
 	setSubName(subName string)
+	getSubName() string
 	setOutputFiles(outputFiles android.Paths)
 }
 
@@ -100,6 +101,10 @@
 	sp.subName = subName
 }
 
+func (sp *BaseSourceProvider) getSubName() string {
+	return sp.subName
+}
+
 func (sp *BaseSourceProvider) setOutputFiles(outputFiles android.Paths) {
 	sp.OutputFiles = outputFiles
 }