Miri stacked borrows improvements for inflate

[folkertdev]

working towards fixing #233

this now works with stacked borrows (the default)

cargo +nightly miri nextest run -p test-libz-rs-sys inflate::

cc @inahga

[codecov]

Codecov Report

Attention: Patch coverage is 97.29730% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
zlib-rs/src/inflate.rs	94.44%	1 Missing ⚠️
zlib-rs/src/inflate/window.rs	97.14%	1 Missing ⚠️
zlib-rs/src/weak_slice.rs	97.05%	1 Missing ⚠️

Files with missing lines	Coverage Δ
zlib-rs/src/allocate.rs	98.98% <100.00%> (+0.02%)	⬆️
zlib-rs/src/inflate/bitreader.rs	90.62% <100.00%> (ø)
zlib-rs/src/inflate/writer.rs	87.66% <100.00%> (ø)
zlib-rs/src/lib.rs	92.98% <ø> (ø)
zlib-rs/src/inflate.rs	95.07% <94.44%> (+<0.01%)	⬆️
zlib-rs/src/inflate/window.rs	97.57% <97.14%> (+0.09%)	⬆️
zlib-rs/src/weak_slice.rs	97.05% <97.05%> (ø)

... and 1 file with indirect coverage changes

[inahga]

Nice!