feat(pick): move pickers to extras (telescope still the default) (#3606)

## What is this PR for?

Refactoring of pickers in LazyVim:

- [x] telescope moved to extras
- [x] dressing was moved to the telescope extra. Not needed with fzf-lua
and noice
- [x] when none of the two is enabled, then telescope will be enabled
- [x] when using `:LazyExtras` to enable fzf-lua, the telescope spec
will never be parsed
- [x] when not using `:LazyExras`, the spec will be parsed, but one of
the two will be disabled.
- [x] only one picker extra can be used to prevent issues
- [ ] cleanup lsp keymaps

lua/lazyvim/util/pick.lua

@@ -12,14 +12,43 @@ local M = setmetatable({}, {
 ---@field buf? number
 ---@field show_untracked? boolean
 
+---@class LazyPicker
+---@field name string
+---@field open fun(command:string, opts?:lazyvim.util.pick.Opts)
+---@field commands table<string, string>
+
+---@type LazyPicker?
+M.picker = nil
+
 ---@type table<string, string>
 M.commands = {
   files = "find_files",
 }
 
+---@param picker LazyPicker
+function M.register(picker)
+  -- this only happens when using :LazyExtras
+  -- so allow to get the full spec
+  if vim.v.vim_did_enter == 1 then
+    return true
+  end
+  if M.picker then
+    LazyVim.warn(
+      "`LazyVim.pick`: picker already set to `" .. M.picker.name .. "`,\nignoring new picker `" .. picker.name .. "`"
+    )
+    return false
+  end
+  M.picker = picker
+  return true
+end
+
 ---@param command? string
 ---@param opts? lazyvim.util.pick.Opts
 function M.open(command, opts)
+  if not M.picker then
+    return LazyVim.error("LazyVim.pick: picker not set")
+  end
+
   command = command or "auto"
   opts = opts or {}
 
@@ -46,8 +75,8 @@ function M.open(command, opts)
       opts.show_untracked = opts.show_untracked ~= false
     end
   end
-  command = M.commands[command] or command
-  M._open(command, opts)
+  command = M.picker.commands[command] or command
+  M.picker.open(command, opts)
 end
 
 ---@param command? string