SI-7852 Omit null check for "".==

Although the same the code would be later optimized by -Yconst-opt,
we can offer the same lean byte code to those compiling without that
option by being more discerning when translating ==.

This helps people using bytecode based code coverage tools
such as jacoco that would emit "branch not covered" warnings
for the impossible null check.
SI-7852 Test to show status quo of for SomeModule.==

For which we can also elide the null check, and will in the
next commit.
SI-7852 Omit null check for Nil.==

For the same reasons outlined in the previous commits.