Move stdlib tests to pos

That way we can compile mixed capture-checked and non-capture checked sources.
Also, add collection/Iterable.scala to test.

We had to add Map as well since there is an incompatibility between the CB sources
(from which we take the tests) and the build binaries (against which they are compiled)
there.

Author: odersky

compiler/test/dotc/pos-test-pickling.blacklist

@@ -27,6 +27,9 @@ i17588.scala
 # Tree is huge and blows stack for printing Text
 i7034.scala
 
+# Causes cyclic reference by interacting with compiler stdlib types
+stdlib
+
 # Stale symbol: package object scala
 seqtype-cycle
 

tests/pos/stdlib/Iterable.scala

@@ -0,0 +1 @@
+collection/Iterable.scala

tests/pos-custom-args/captures/stdlib/IterableOnce.scala renamed to tests/pos/stdlib/IterableOnce.scala

@@ -0,0 +1 @@
+collection/Map.scala