This also changes the fuzzing infrastructure from proptest to cargo-fuzz,
and this lead to the discovery of two mishandlings of edge-cases:
* when a "path_to_store" is at the end of the input, it tried to access
the input slice out-of-bounds (the `just_store` test covers that now)
* non-ASCII characters lead to an out-of-bounds access in HalfBytesMask
(the `non_ascii` test covers that now)
Change-Id: Icaa2518dcd93e1789a2c0da4cf0fec46016d3bad
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4604
Tested-by: BuildkiteCI
Reviewed-by: zseri <zseri.devel@ytrizja.de>
