Quantizer rdo and heuristic quantizer selection causes desync

[ycho]

Originated from #1858 and #1914.

Two commits that cause desync at speed 0,1,2 are:
3c79e02 and
db0da3c
those might cause the desync from different origins, but given that temporary fix of disabling segmentation (as in #1914) indicates that encoding of segment id might cause issue.

A set of test runs to see desync that I used can be:
./target/release/rav1e nyan.y4m -o test.ivf -r test_rec.y4m --quantizer 50 --speed=0 --limit=30
./target/release/rav1e nyan.y4m -o test.ivf -r test_rec.y4m --quantizer 50 --speed=1 --limit=30
./target/release/rav1e nyan.y4m -o test.ivf -r test_rec.y4m --quantizer 50 --speed=2 --limit=30

Note that the desync happens regardless of --tune.

[ycho]

Fixed by #1977
Not merged but alternative minimum fix (for reference purpose) is:
ycho@a8f10af
in
https://github.com/ycho/rav1e/tree/3eb666a8eab_fix0