General audit of range length/remaining definitions and usage

[pineapplemachine]

Not a comprehensive list of issues:

Many ranges still lack a remaining property even where one should be valid.

The length property of heaps (which are also ranges) would be better described as remaining for a range.

The asarray implementations should refer to remaining rather than length when determining how many elements to expect.

[pineapplemachine]

This has currently been accomplished for most - but not all - packages in mach.range as part of a general cleanup and documentation effort.