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: Iab077f256ff3776495302606572f384d82ab171f
Merged-In: Iab077f256ff3776495302606572f384d82ab171f
(cherry picked from commit 4a8876ec9e6282d452f7a03f69a78512d65648f0)
(cherry picked from commit e3ceaed976e3cc4cc86ac1fb3e7b74dac833b264)
4 files changed