Detect detach/attach in same observation (alt)

[kurkle]

Alternative to #9876

This approach keeps one observer the whole time and fires attach/detach every time encountered.

pros

• less duplication
• every attach / detach is detected
• should ensure chart is resized if detached and immediately attached to different sized container

cons

• every attach / detach is detected

[kurkle]

Filename	Size	Change
dist/chart.esm.js	73.1 kB	+11 B (0%)
dist/chart.js	92.4 kB	+12 B (0%)
dist/chart.min.js	65.6 kB	-10 B (0%)

[etimberg]

This change looks ok. I'm not sure which is better compared to #9876

[kurkle]

As #9876 was verified to be working for at least one use case, I'm closing this in favor of that.