Debugger MemoryViewWidget: always highlight target address

[TryTwo]

Highlighting wasn't doing much before. Now it lets you know what address is being targeted. The colors can be changed, I just set it to normal. A stylesheet needed to be used, or else the selected item coloring is removed when focus is lost, which isn't good.

There is also a thin outline box on whatever cell you click, without changing the highlighting on the target.

I'm not sure if set focus is needed anymore, but it seemed a little broken when the table was given the slider navbar, so I fixed that. I think it was mostly a highlighting thing, but then I overrode the highlighting altogether.

[sepalani]

Tested and LGTM. The behaviour on this PR is more intuitive than the current Dolphin's one. The selected cell stays highlighted during scrolls. The right click options seem to still work as intended.

[TryTwo]

I noticed if you put a misaligned address in, nothing gets highlighted. I'm not sure if that's good behavior or if it should align down.

[sepalani]

I noticed if you put a misaligned address in, nothing gets highlighted. I'm not sure if that's good behavior or if it should align down.

IMO, I think that's fine. The issue doesn't appear when no alignment is set. If the current behaviour isn't considered as fine, you should check the highlight address boundary with the display type size or align down m_address_highlight. For the latter, you should make sure you don't "loose" precision when changing back and forth from display type with the right/wrong alignment.

[TryTwo]

Ok, I'll just leave it, so it doesn't give the wrong idea.