Make it easier to run tests locally

Certain tests could break if you ran them separately from other tests.
They have been patched.

`run-tests` now has a `--fast` option which runs tests with only the
fastest Vim version ALE tests with, and the custom checks.

test/handler/test_glslang_handler.vader

@@ -1,3 +1,6 @@
+Before:
+  runtime ale_linters/glsl/glslang.vim
+
 Execute(The glsl glslang handler should parse lines correctly):
   AssertEqual
   \ [