TWKB generations works too much on the heap

[pramsey]

Checking a profile of TWKB it becomes pretty clear that for large numbers of small objects it spends an inordinate amount of time allocating and deallocating memory, mostly handling bytebuffers on the heap. Sticking those buffers on the stack, and also having the buffers use a default static buffer initially makes things *much* faster.

[pramsey]

In 15780:

Improve TWKT performance by avoiding lots of allocations
on the heap. (Closes #3855)

[robe]

all this work and no NEWS update or Doc update?

Shouldn't this be under section enhancements?

[robe]

In 15795:

Note twkb improvements in docs.
Closes #3855