fix(options): ":set foo?" for Lua callbacks #41100

Problem:
`:set foo=<tab>` and `:set foo?` for func/expr options set to a Lua
function, always displays "v:lua".

The existing "<Lua N: file:line>" form was avoided because the ref id
N changes on every read of the same option.

Solution:
- Don't attempt to tab-complete Lua functions.
- Show "<Lua file:line>" (or "<Lua>" if source file is unknown).

Example:

    :set operatorfunc?
      operatorfunc=<Lua ~/.config/nvim/init.lua:42>

0 files changed, 0 insertions, 0 deletions