Rename bzl files to scl These files don't have anything to do with bazel, they just use starlark as a configuration language. Bazel recently introduced the scl file extension to use for this format, which doesn't have any bazel-specific symbols. Use that extension for our pure starlark files as well. Bug: 309686282 Test: Presubmits Change-Id: Ic17eff0b97bcb7584a7f9afaef2e470887362e18