[PERFORMANCE] Fix Memory Leaks caused by EditorVariableWaveform + Optimize it

[menvae]

Changes

• EditorVariableWaveform is now a BufffedContainer and we use .CreateView to draw it.
  • This means we only need to ever instantiate once and use it wherever without any performance costs
  • on the topic of performance:
    • Waveform is only drawn only when it's needed such as when time in clock changes or any drawable is actually rendering it. but it has to be manually untracked since OnDispose is internal and we don't untrack on all cases of dispose as is the case of PointListEntry
• Created an OnClose virtual method in PointListEntry to know when point is closed. This is needed for untracking the point for the waveform when closing.

We track the drawables to know if it is IsPresent so we know to not render the waveform if any of the consumers aren't even rendered themselves.

FIxes #247