Import resolution now gradually resolve qualified names one step at a
time to exclude cases when parent and child modules are resolved from
different source roots.

The shortcuts are based on our common shortcuts set dependent on the
selected keymap.

platform: restore throwing exception when creating Single/MultipleRootFileProvider for injected contents

Review ID: IDEA-CR-29835

Fixes some failing cases of target replacement (IDEA-146380)

because some packages like mypy can actually install their resources
there, and it breaks our detection of built-in and third-party packages.
On Windows this check doesn't make sense since there site-packages
and copied stdlib modules lie directly inside "Lib", i.e. there is no
additional level of nesting.

while deciding whether we should use the bundled virtualenv or venv
module of Python 3.3+. Previously we incorrectly thought that every
detected interpreter has the default 2.7 version, since this kind
of interpreter doesn't store its version when discovered.

IDEA-181303 java.lang.IllegalArgumentException by org.jetbrains.org.objectweb.asm.ClassVisitor while running JUnit tests with latest EAP