Implement sheared text box with filter count and use in multi/playlists lounge

[Joehuu]

To be used in song select redesign also, but demonstrating it in playlists/multi as that has the newer OverlayColourProvider/sheared design, and may look out of place in current song select design:

Unsure about the code. Made a separate ShearedFilterTextBox instead of incorporating it into the base as there may be cases where the filter count doesn't make sense. Like maybe ModSelectOverlay unless it makes sense to add the count there too.

[peppy]

That vertical caret looks so out of place... at very least it needs more padding, at most it needs actual design thought (I assume an active state was not included in the design, so this should be added / provided cc @arflyte).

[bdach]

Caret is one thing but I'm not sure what this alignment is supposed to be in general:

It's so disjointed. Nothing is aligned to anything. Why is the count text further away from the edge rather than closer to follow the shearing?