menuconfig: Make search more flexible and search prompts

This commit gets the following incremental search improvements in from
upstream:

  - 1d3db5de9b8c2 ("menuconfig: Add search with multiple search
    strings")

    This makes a search string like 'foo bar' match all symbol names
    that match both 'foo' and 'bar' (which can be regexes), regardless
    of the order in which they appear in the match. This is faster and
    more flexible than having to type a bunch of '.*'.

  - 9bf8fc6e6907e ("menuconfig: Add prompts to incremental search")

    This makes the incremental searcher search prompt strings as well as
    symbol names.

    The prompt is now displayed next to the symbol name in the list of
    matches as well.

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>