New Imbalance Tables Tweak

[FauziAkram]

Imbalance tables tweaked to contain MiddleGame and Endgame values, instead of a single value.

The idea started from Fisherman, which requested my help to tune the values back in June/July, so I tuned the values back then, and we were able to accomplish good results, but not enough to pass both STC and LTC tests.

So after the recent changes, I decided to give it another shot, and I am glad that it was a successful attempt.

A special thanks goes also to mstembera, which notified me a simple way to let the patch perform a little better.

Passed STC:
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 115976 W: 23124 L: 22695 D: 70157
Ptnml(0-2): 2074, 13652, 26285, 13725, 2252
https://tests.stockfishchess.org/tests/view/5fc92d2d42a050a89f02ccc8

Passed LTC:
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 156304 W: 20617 L: 20024 D: 115663
Ptnml(0-2): 1138, 14647, 46084, 15050, 1233
https://tests.stockfishchess.org/tests/view/5fc9fee142a050a89f02cd3e

Bench: 4278746

[vondele]

@FauziAkram thanks for the patch.

For future patches, can you make sure to make your pull requests as a single commit, including the right bench? The trick with modifying the AUTHORS file is a bit of a workaround. You'll need to read up on git rebase -i. A typical workflow would be like:

#go to branch
git checkout imbl2
# create a new branch for this PR
git checkout -b impbl2PR
# rebase on current master
# use r (reword) for the first commit (adjust commit message with STC and LTC results)
# use f (fixup) for the latter commits
git rebase -i master
# test compile / get bench
make -j ARCH=x86-64-modern build && ./stockfish bench
# final adjustment of commit message, with correct bench
git commit --amend
# publish for PR
git push origin impbl2PR

now do a pull request with impbl2PR