Renderscript: rename .rs extension to .rscript

Reserve .rs extension for Rust.

Bug: 137365032
Test: make checkbuild
Test: cd frameworks/compile/slang/tests
    ./slang_tests.py
    Test: atest CtsRenderscriptTestCases
    Test: CtsRsCppTestCases

Exempt-From-Owner-Approval: Clean CP
Change-Id: I0458009b8bb64a012fece364835d5b78d52e15e9
Merged-In: I0458009b8bb64a012fece364835d5b78d52e15e9
(cherry picked from commit 41ce1c0d82)
(cherry picked from commit a50b16974a)

cc/compiler.go

@@ -485,7 +485,7 @@ func (compiler *baseCompiler) compilerFlags(ctx ModuleContext, flags Flags, deps
 			"-I"+android.PathForModuleGen(ctx, "aidl").String())
 	}
 
-	if compiler.hasSrcExt(".rs") || compiler.hasSrcExt(".fs") {
+	if compiler.hasSrcExt(".rscript") || compiler.hasSrcExt(".fs") {
 		flags = rsFlags(ctx, flags, &compiler.Properties)
 	}