Create module 'builtins', move 'runtime' -> 'runtime.jvm'

'builtins' will be used for platform-independent core built-in definitions,
'runtime.jvm' for things that should be present at runtime in order for Kotlin
code to execute correctly on JVM

ProgressionUtil goes to 'builtins' right now because progression iterators
depend on it, but should be rewritten to Kotlin later
Generate Kotlin sources of progression iterators
Remove duplicated sources of built-ins

BuiltInsSerializer now serializes built-ins found in two source roots:
core/builtins/native and core/builtins/src

Add return types to some declarations in core/builtins/src, because now that
BuiltInsSerializer processes them, it launches lazy resolution which can't
always deduce the return type
Don't fail on annotated built-ins

Unit.VALUE is annotated right now (with "suppress"), so deserialization was
throwing an exception from AnnotationDeserializer.UNSUPPORTED. Return empty
collections of annotations instead; here we use the fact that it's the only
annotation in built-ins and its presence is useless to the type checker
Update test data after introduction of compilable built-ins

'next()' in primitive iterators is now final, as it always was in module
'runtime' before
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