slabtop: implemented tui

[Krysztal112233]

fix #190

This pr also implemented refresh by space and exit by q, but not implemented -o flag: due to performance considerations, only a portion of the list will be rendered at this time.

[cakebaker]

Yep, there is definitely some performance issue, it constantly uses ~70% of CPU on my machine ;-)

[Krysztal112233]

CPU usage is now reduced by slowing down the redraw speed, but redrawing is still triggered once the window size is changed.

But I think it's as expected, as it avoids confusing TUI output :)

[Krysztal112233]

Hi, this pr has been finished for a long time. I've reorganized the commits and could you have a look about it? :)

@cakebaker @sylvestre

[cakebaker]

It looks like you added some unrelated stuff with your latest commit :|

[Krysztal112233]

After much deliberation I'm going to close this pr: procps-ng seems to be in the process of completely rewriting its TUI.

[cakebaker]

Hm, where do you see that they are rewriting the TUI? As far as I can see the latest commit related to slabtop was in April and that was a minor UI change, increasing column sizes.

[Krysztal112233]

I noticed that the top command in procps-ng has almost completely rewritten the TUI. @Bluemangoo reminded me that top now has a more modern TUI, so I think we may not need to stick strictly to the original interface. Also, the quality of this PR doesn't look very high right now, so I plan to create a new PR to implemented the TUI of slabtop.