feat(ui): use vim.ui.select for :tselect, z= #39478

Problem:
`:tselect` and `z=` (spell suggest) have their own bespoke select menus.

Solution:
- Delegate to `vim.ui.select` instead.
- Bonus:
  - `:tselect` gains mouse support. `print_tag_list` didn't suport mouseclick.

This causes some minor regressions, which are not blockers:

- `z=` no longer draws the list right-left if 'rightleft' is set.
  - TODO: can/should `vim.ui.select` / `vim.fn.inputlist()` handle that?
- `:tselect`
  - No "column" headings (`# pri kind tag file`).
  - No highlighting: (HLF_T: tag name, HLF_D: file, HLF_CM: extra fields).
  - TODO: can `vim.ui.select()` support highlighted chunks (`[[text, hl_id], ...]`) ?

fix https://github.com/neovim/neovim/issues/25814
fix https://github.com/neovim/neovim/issues/31987

test/functional/lua/ui_spec.lua

@@ -2,7 +2,6 @@ local t = require('test.testutil')
 local n = require('test.functional.testnvim')()
 
 local eq = t.eq
-local pcall_err = t.pcall_err
 local ok = t.ok
 local exec_lua = n.exec_lua
 local clear = n.clear
@@ -17,41 +16,6 @@ describe('vim.ui', function()
     clear({ args_rm = { '-u' }, args = { '--clean' } })
   end)
 
-  describe('select()', function()
-    it('can select an item', function()
-      local result = exec_lua [[
-        local items = {
-          { name = 'Item 1' },
-          { name = 'Item 2' },
-        }
-        local opts = {
-          format_item = function(entry)
-            return entry.name
-          end
-        }
-        local selected
-        local cb = function(item)
-          selected = item
-        end
-        -- inputlist would require input and block the test;
-        local choices
-        vim.fn.inputlist = function(x)
-          choices = x
-          return 1
-        end
-        vim.ui.select(items, opts, cb)
-        vim.wait(100, function() return selected ~= nil end)
-        return {selected, choices}
-      ]]
-      eq({ name = 'Item 1' }, result[1])
-      eq({
-        'Select one of:',
-        '1: Item 1',
-        '2: Item 2',
-      }, result[2])
-    end)
-  end)
-
   describe('input()', function()
     it('can input text', function()
       local result = exec_lua [[