The goal is to support better search experience in the cases where we want to
explicitly influence the ordering instead of relying only on general heuristics.
We used to support this already at some point I think, but not anymore since we
started using menu-search.
The implementation is fairly straight forward. It mainly just forwards the
search weight from the menu definition to the search code through various
required steps. The main annoying thing is that changing the signature of e.g.
`uiItemFullO_ptr` is fairly involved. Even using default parameters for these
functions is a bit annoying and becomes fairly unreadable and error-prone on the
call-site. For now, I worked around this by storing the search weight on the
`uiLayout` and to copy it to the `uiBut` from there. That seems preferable until
we have a better solution for adding parameters to all the `uiItem*` functions.
Pull Request: https://projects.blender.org/blender/blender/pulls/120572
d1634b2a4a