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: I33010b5604d8140f3a50845c16daff743504c8d0
Merged-In: I33010b5604d8140f3a50845c16daff743504c8d0
(cherry picked from commit fafc72bd8b)
(cherry picked from commit 86fdb97cbb)

cmds/stagefright/Android.mk

@@ -153,9 +153,9 @@ include $(BUILD_EXECUTABLE)
 include $(CLEAR_VARS)
 
 LOCAL_SRC_FILES:= \
-        filters/argbtorgba.rs \
-        filters/nightvision.rs \
-        filters/saturation.rs \
+        filters/argbtorgba.rscript \
+        filters/nightvision.rscript \
+        filters/saturation.rscript \
         mediafilter.cpp \
 
 LOCAL_SHARED_LIBRARIES := \