Add -check-all option to test everything required by a module

You can now run with -check-all, and all imported modules will be run as well
for their tests.  So, for example, to test the compiler's check blocks, which
hits desugar and the various ASTs, you can run:

node build/phase1/main-wrapper.js \
  --module-load-dir build/phase1/arr/compiler/ \
  -check-all src/arr/compiler/compile.arr