Vim9 LSP setup

Here's a suggestion (see also https://github.com/yegappan/lsp/pull/562) how to set up Vista to use this LSP when available and otherwise fall back to ctags:

vim9script
augroup LspSetup
  autocmd!
augroup END
g:lspFiletypes = []
for i in range(len(g:lspServers))
  for ft in g:lspServers[i].filetype
    add(g:lspFiletypes, ft)
    # Only set workspace root once the first file of that file type is openend
    # otherwise the workspace root often is $HOME and the LS scans too many files
    exe 'autocmd LspSetup FileType' ft '++once'
          \    'autocmd LspSetup BufWinEnter <buffer> ++once call LspAddServer([g:lspServers[' .. i .. ']])'
  endfor
endfor

nnoremap <expr> dp &l:diff ? 'dp' : ':<c-u>Vista show<cr>'
let g:vista_executive_for = {}
for i in range(len(g:lspServers))
    for ft in g:lspServers[i].filetype
        call extend(g:vista_executive_for, { ft : 'yegappan_lsp' })
        exe 'autocmd vimrc FileType' ft 'nnoremap <buffer><expr> dp &l:diff ? "dp" : ":<c-u>Vista!!<cr>"'
    endfor
endfor