perf config: Add annotate.demangle{,_kernel}

Committer notes:

This allows setting this in from the command line:

  $ perf config annotate.demangle
  $ perf config annotate.demangle=yes
  $ perf config annotate.demangle
  annotate.demangle=yes
  $ cat ~/.perfconfig
  # this file is auto-generated.
  [report]
  	sort-order = srcline
  [annotate]
  	demangle = yes
  $
  $
  $ perf config annotate.demangle_kernel
  $ perf config annotate.demangle_kernel=yes
  $ perf config annotate.demangle_kernel
  annotate.demangle_kernel=yes
  $ cat ~/.perfconfig
  # this file is auto-generated.
  [report]
  	sort-order = srcline
  [annotate]
  	demangle = yes
  	demangle_kernel = yes
  $

Signed-off-by: Martin Liška <mliska@suse.cz>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/c96aabe7-791f-9503-295f-3147a9d19b60@suse.cz


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>