Fixup rangebreaks l2p and p2l functions

[archmoj]

Following of #4614,
this PR fixes l2p & p2l functions

• correct reversed ranges fixesrangebreaks mapping on reversed ranges #4700
  see 11c8ea2?short_path=563a470#diff-563a470dab197f9857d9545f11805d89

• find correct hover indices and fixesrangebreaks hovermode=closest offset #4693
  Hover demo: before vs after
  Hover demo2: bar + reversed range

@plotly/plotly_js

[alexcjohnson]

What's going on with autorange in axes_breaks-night_autorange-reversed.png ? Both the orange and red subplots prior to this PR have tight clipping on one side, and after this PR the tight clipping is on the other side. Neither side should have tight clipping, they should both get 5% padding. Also what's with the label 23:22 that's in the same place both before and after this PR, despite the axis range changing?

[alexcjohnson]

l2p is a hot path, so it's worth optimizing a good deal - even if it means some duplicated code, though I'm not sure if that would help here, and even if the code needs more comments and is less self-documenting. For example:

• signAx * pos could be done once up front, and var min = signAx * brk.min etc would simplify these conditionals a bit
• first and last look unnecessary
• Flip _m2 for y axes after using it to calculate _B, so we don't need the (isY ? -1 : 1) * down below.
• Move var isY = axLetter === 'y' to the outer scope, where axLetter was defined.

p2l I think is generally not as hot, though maybe for some traces it's used in hover? Not sure. (Note that c2p uses l2p and p2c uses p2l)

[archmoj]

Good calls. Addressed in the commits below.

[archmoj]

What's going on with autorange in axes_breaks-night_autorange-reversed.png ? Both the orange and red subplots prior to this PR have tight clipping on one side, and after this PR the tight clipping is on the other side. Neither side should have tight clipping, they should both get 5% padding. Also what's with the label 23:22 that's in the same place both before and after this PR, despite the axis range changing?

Fixed by 749430d.

[alexcjohnson]

Excellent work! 💃