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

cc/test.go

@@ -173,7 +173,7 @@ func TestPerSrcMutator(mctx android.BottomUpMutatorContext) {
 		if test, ok := m.linker.(testPerSrc); ok {
 			numTests := len(test.srcs())
 			if test.testPerSrc() && numTests > 0 {
-				if duplicate, found := checkDuplicate(test.srcs()); found {
+				if duplicate, found := android.CheckDuplicate(test.srcs()); found {
 					mctx.PropertyErrorf("srcs", "found a duplicate entry %q", duplicate)
 					return
 				}
@@ -206,17 +206,6 @@ func TestPerSrcMutator(mctx android.BottomUpMutatorContext) {
 	}
 }
 
-func checkDuplicate(values []string) (duplicate string, found bool) {
-	seen := make(map[string]string)
-	for _, v := range values {
-		if duplicate, found = seen[v]; found {
-			return
-		}
-		seen[v] = v
-	}
-	return
-}
-
 type testDecorator struct {
 	Properties TestProperties
 	linker     *baseLinker