feat: show assigned function in actions.which_key

[fdschmidt93]

Out of laziness, I now left action_mt docs out, because their main purpose otherwise (apart from originally for which_key) I suppose is sufficiently described in :h telescope.actions

Works as intended in my tests. If you don't like it @Conni2461 , it's totally fine 😅 felt like a challenge and my experiments are running on GPUs now anyways.

Closes #1869

My test code

local builtin = require("telescope.builtin")
local actions = require("telescope.actions")
local action_state = require("telescope.actions.state")

local M = {}

M.print_prompt = function(prompt_bufnr)
  local current_picker = action_state.get_current_picker(prompt_bufnr)
  current_picker:_get_prompt(value)
  print(prompt)
end

function print_value(prompt_bufnr)
  local value = action_state.get_current_history().value
  print(value)
end

local say_hi = function(prompt_bufnr)
  print("hi")
end

builtin.find_files({
  attach_mappings = function(prompt_buf, map)
    map("i", "X", function()
      print("test")
    end)
    map("i", "p", M.set_prompt)
    map("i", "P", print_value)
    map("i", "H", say_hi)
    map("i", "O", require "fds.utils".resize)
    return true
  end,
})

[Conni2461]

Lets make this the last commit part of the 0.6 tag

Thanks :) LGTM

[Conni2461]

Oh yeah. I write docs/spec for actions.mt.

Me mentioning it that we should do it, was not like me asking you to do it. If that makes sense 😆