feat(lsp): add 'focus' option to open_floating_preview (#16465)

When the 'focusable' and 'focus_id' parameters are set,
`open_floating_preview` assumes that it should always move focus to an
existing floating window with the same 'focus_id'. However, there are
cases where we want to make a floating window focusable, but do not want
to focus it upon calling `open_floating_preview`. To distinguish these
cases, add a boolean parameter 'focus' that, when false, prevents
moving focus.

runtime/lua/vim/diagnostic.lua

@@ -520,7 +520,7 @@ local function diagnostic_move_pos(opts, pos)
         vim.api.nvim_win_get_buf(win_id),
         vim.tbl_extend("keep", float_opts, {
           scope = "cursor",
-          focusable = false,
+          focus = false,
         })
       )
     end)