Add rust_test and rust_test_host.

* Rust tests are like binary files compiled with --test.
  New test.go follows binary.go code patterns and reuses
  some code in binary.go.
* Generate one test per source file as testPerSrc in cc/test.go.
  The "all tests" variation feature of cc/test.go is not copied yet.
  Fix some Stem and SubName settings to make testPerSrc work.
* Move cc.CheckDuplicate to android.CheckDuplicate,
  which is now shared by cc and rust.
* Refactor tests in binary_test.go and add new test_test.go.

Bug: 140938178
Test: mm in rust projects, added rust_test and rust_test_host
Change-Id: Ia6fec8b4cf2572fd352ab1938a1f3c7b5cca2212
diff --git a/rust/testing.go b/rust/testing.go
index cd63084..24defa6 100644
--- a/rust/testing.go
+++ b/rust/testing.go
@@ -168,6 +168,8 @@
 	ctx.RegisterModuleType("cc_object", android.ModuleFactoryAdaptor(cc.ObjectFactory))
 	ctx.RegisterModuleType("rust_binary", android.ModuleFactoryAdaptor(RustBinaryFactory))
 	ctx.RegisterModuleType("rust_binary_host", android.ModuleFactoryAdaptor(RustBinaryHostFactory))
+	ctx.RegisterModuleType("rust_test", android.ModuleFactoryAdaptor(RustTestFactory))
+	ctx.RegisterModuleType("rust_test_host", android.ModuleFactoryAdaptor(RustTestHostFactory))
 	ctx.RegisterModuleType("rust_library", android.ModuleFactoryAdaptor(RustLibraryFactory))
 	ctx.RegisterModuleType("rust_library_host", android.ModuleFactoryAdaptor(RustLibraryHostFactory))
 	ctx.RegisterModuleType("rust_library_host_rlib", android.ModuleFactoryAdaptor(RustLibraryRlibHostFactory))
@@ -190,6 +192,7 @@
 
 		// rust mutators
 		ctx.BottomUp("rust_libraries", LibraryMutator).Parallel()
+		ctx.BottomUp("rust_unit_tests", TestPerSrcMutator).Parallel()
 	})
 	bp = bp + GatherRequiredDepsForTest()