Update menuconfig (and Kconfiglib, just to sync) to upstream revision
256e5b3e38e92 to get the fix below in, for an issue in an external
project. Also update genrest.py with a similar fix (the genrest issue
was what originally prompted it).
menuconfig: Improve/fix promptless choice handling
The code assumed that all parent (interface) menus always have a
prompt, which is false for items in promptless choices. This led to
a crash e.g. when viewing the symbol information for a symbol within
a promptless choice.
Promptless choices with children can show up "legitimately" when
people define choices in multiple locations to add symbols, though
this is broken in the C tools.
Use standard_sc_expr_str(node.item) instead of the non-existing
prompt for promptless choices. That way they show up as
'<choice (name if any>)>', which is consistent with how they're
shown elsewhere.
This commit also changes how choice names are displayed in
show-name/show-all mode, to the standard_sc_expr_str() format.
Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>