SI-7852 Omit null check for SomeModule.==

For the same reasons outlined in the previous commits.
SI-7852 Refactor null-elision tests to be more focussed

 - Directly count null checks, rather than diffing the textual
   bytecode of the entire method
 - Add a test to show that the LHS needs to be a direct module
   reference, not just a tree with a module type, to elide the
   null check.