fix: check existing_client support workspaceFolder

[glepnir]

if existing_client does not support workpaceFolder should spawn a new server instance

[lithammer]

This looks like something that should be upstreamed to core?

[glepnir]

reuse_client just a condition check in the upstream. Maybe other possibilities are considered as public API. Not sure if coding check workpaceFolder in core is appropriate. But we need it here because it is compatible with release version

function lsp.start(config, opts)
  opts = opts or {}
  local reuse_client = opts.reuse_client or reuse_client_default
  local bufnr = resolve_bufnr(opts.bufnr)

  for _, client in pairs(all_clients) do
    if reuse_client(client, config) then
      if lsp.buf_attach_client(bufnr, client.id) then