Add "Settings" link under "Network Admin" toolbar menu

[johnjamesjacoby]

Of all the top level network menu items represented in the toolbar, "Settings" is omitted. This was intentional 2 or 3 years ago, but I'd like to revisit this specifically again.

In a multi-network installation, the network settings page is (anecdotally) visited about as frequently as site settings is. Once everything is configured, it's rare to need to go back there, but I think the same goes for network plugins & themes, too.

Setting the version to 3.4, since that was the last time (that I can find) that this was discussed. Patch imminent.

[johnjamesjacoby]

Add "Settings" toolbar menu-item in wp_admin_bar_my_sites_menu()

[johnjamesjacoby]

Related: #21674

[johnjamesjacoby]

Highlighting new "Settings" toolbar menu-item

[johnjamesjacoby]

If we decide (again) that this isn't a worthy addition, I don't mind adding this to to the WP Multi Network plugin instead. The only issue there would be the possibility of having a duplicate "Settings" menu-item for the audience of users that are currently using in multi-network setups if we decide to introduce this into WordPress core in the future.

[johnbillion]

+1. Even if it's not frequently visited, it's the only top level network admin menu item that isn't present in this menu. Let's add it for consistency.

Also +1 on the -o suffix for options.

[jeremyfelt]

In 35156:

MS: Add "Settings" link under "Network Admin" toolbar menu.

Props johnjamesjacoby.
Fixes #34287.