compiletest: rename "runtest/crash.rs" to "runtest/crashes.rs" to be in line with the test directory

r? jieyouxu

Author: matthiaskrgr

src/tools/compiletest/src/runtest.rs

@@ -39,7 +39,7 @@ mod assembly;
 mod codegen;
 mod codegen_units;
 mod coverage;
-mod crash;
+mod crashes;
 mod debuginfo;
 mod incremental;
 mod js_doc;