Store mode on the stack in dispatch

[bjorn3]

This improves performance for chunk size 2^4 by a couple percent.

[codecov]

Codecov Report

Attention: Patch coverage is 87.87879% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
zlib-rs/src/inflate.rs	87.87%	8 Missing ⚠️

Files with missing lines	Coverage Δ
zlib-rs/src/inflate.rs	91.20% <87.87%> (+0.03%)	⬆️

... and 2 files with indirect coverage changes

[bjorn3]

https://github.com/trifectatechfoundation/zlib-rs/actions/runs/13524557151

[bjorn3]

I had to do this rewrite while experimenting with adding #[loop_match] in zlib-rs. I noticed that even before I started using #[loop_match] this improved performance.

[folkertdev]

with the comment