Bug: Inability to solve full-board #3 (motivation for PR #360)

[JoshuaGreen]

In PR #360, @MuTsunTsai wrote:

This PR is motivated by the following problem:

fors krbrqqqq/rbqsbrbq/qrbsqsbr/qqqrbsqb/qqqqqrbr/qqqqqqbS/brqqqqqq/Kbqqqqqq
stip #3

It has a solution 1.Nxg5!, but in some environments (namely wasm and certain MacOS builds) it has been reproduced that Popeye failed to find the solution.

It's worth tracking this as an Issue.

[JoshuaGreen]

feature/tighten_hash_usage is an independent attempt to correct this issue based on the initial idea in PR #360, increasing the size of hashbuf_length (but in a systematic way) while making a number of other improvements to the hash infrastructure and increasing MaxPieceId.