kconfiglib: Record which MenuNode has each property

This commit does some major surgery to Kconfiglib so that properties
(defaults, selects, etc.) can be shown on the menu node that actually
has the propetrty for symbols and choices defined in multiple locations.

This will be used to improve the output of genrest.py and the symbol
information display in the menuconfig.

The parsing code is a bit simpler now too as a side effect.

Commit message from Kconfiglib (63a44186137e2)
==============================================

This allows accurate documentation to be generated for symbols and
choices defined in multiple locations. There are now MenuNode.defaults,
MenuNode.selects, etc., lists that mirror the corresponding
Symbol/Choice lists.

Symbol/Choice.__str__() now correctly show property locations as well,
by simply concatenating the strings returned by MenuNode.__str__() for
each node.

_parse_properties() was modified to add all properties directly to the
menu node instead of adding them to the contained symbol or choice. The
properties are then copied up to symbols and choices in
_finalize_tree(). Dependency propagation is handled at the same time.

As a side effect, this cleans up the code a bit and de-bloats
_parse_properties().

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>