[tooltip] fix tootlip with bounds offset

[williaster]

🐛 Bug Fix

This PR fixes a pretty bad and somewhat esoteric bug for <TooltipWithBounds /> in the @vx/tooltip package. Since my PR that introduced optional padding/offsets for this component, it's been acting weird on the edges of containers:

@conglei and I debugged this earlier today and what we think is happening is that the tooltip width is being compressed on the edge of charts (when word-wrap is set to allow wrapping) like the pic below, making its width smaller and height larger (note this gif has boundary detection disabled).

This smaller width and larger height are reflected in the withBoundingClientRects we get, but it seems because the tooltip is actually offset from the edge of the chart it does not visually appear to change dimensions. This means that our calculation for the offset includes a smaller-than-actual-width and larger-than-actual-height, making the tooltip go all over (if you pay close attn to the broken gif, it's consistent with this).

The fix was to switch to using css transforms instead of top and left. We set top to 0 meaning that the withBoundingClientRects dimensions are always in sync with the rendered tooltip:

cc @techniq

[techniq]

LGTM, and should have better perf by not requiring a layout or paint (https://csstriggers.com/transform) although I haven't benchmarked it.

[hshoff]

LGTM