~ returned protected-modifiers to MethodTransformer methods
~ fixed nullability mess
~ simplified isInlineMarker* methods
~ minor semicolon
~ typo in assert
~ naming fixes: count -> amount
~ reduced instructions-list traversing passes count
~ Minor, use stack from com.intellij.util.containers
OptimizationBasicInterpreter: merging primitives

If merging primitives of different types (e.g. I and Z)
return the first one instead of MIXED_VALUE type
because MIXED_VALUE only should work for objects