CompilerControl.askTypeAt(pos) should return the chain of parents containing pos, and not only the innermost tree

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Based on a this discussion related to both #5064 #8125, it was suggested by Iulian that CompilerControl.askTypeAt(pos) would be changed so that it returns the whole chain of parents (with an opaque range position) that include the passed pos.

Benefits:

1. No need to create opaque range position for Trees that should really have a transparent positions. This discussion should prove the point.

2. The solution is general enough, and will reduce code duplication, as there are several places in the IDE codebase where we need to access the parent of a Tree.

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Imported From: https://issues.scala-lang.org/browse/SI-8136?orig=1
Reporter: @dotta
Affected Versions: 2.11.0-M7

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@dotta said:
scala/scala#3358