Refactor CompileKotlinAgainstCustomBinariesTest

Make all filenames start with lowercase letter (instead of half lower / half
upper)
Minor, package "test" in compileJavaAgainstKotlin testData
Minor, fix typo in diagnostic message
Fix annoying parameter name override warning

Some corner cases still remain: KotlinSignature, propagation, deserialized
delegates to Java interfaces

 #KT-1239 Obsolete
 #KT-1924 In Progress
 #KT-2081 Fixed
Support hasStableParameterNames in KotlinSignature and propagation

 #KT-1924 In Progress
 #KT-2830 Fixed
Disallow named arguments for Java methods

Since they don't have stable names: they're (sometimes) loaded from the
bytecode, which (sometimes) doesn't contain parameter names