x/tools/gopls: extract func/method arg(s) to struct

[danp]

Given something like this, where timeout is an option:

func search(query string, timeout time.Duration) {}

When it's time to add another option, one might extract timeout to an options struct so it's then easy to add more things:

type searchOptions struct {
  timeout time.Duration
}

func search(query string, opts searchOptions) {}

A code action for this kind of extraction would be very helpful!