[maxfischer2781]

This MR fixes various bugs related to sorting items. Major changes include:

• The max/min and heapq.merge code now correctly sorts equal or uncomparable (e.g. nan) items (closes [Bug]: max returns the last tied item instead of the first #235)
  • A shortcut implied "not a < b" is equal to "a > b". It now correctly uses "b < a" in place of "a > b".
  • heapq.merge now only uses not a < b and not b < a if a == b is undefined
  • The reliance on < (instead of >) is in line with Python's standard sort features. For example, list.sort "[…] sorts the list in place, using only < comparisons between items."
• The max/min no longer applies the key function to the default (closes [Bug]: min and max evaluate key on an empty-input default #237)
  • default is only ever used if no comparison is needed
  • Updated docs stenotypes to match code type hints
• heapq.merge(..., reverse=True) no longer reverses the ordering of the iterators themselves (closes [Bug]: Descending merge reverses equal-key source order #234)
• Removed leaky optimisation of sorted that could hide TypeErrors from comparisons (closes [Bug]: sorted swallows TypeError from synchronous generators #236)