LongArrayBitVector reader and writer in Rust

[progval]

Hey,

Just so you know, I wrote a Rust reader and writer of the Java serialization of it.unimi.dsi.bits.LongArrayBitVector here:

https://gitlab.softwareheritage.org/swh/devel/swh-graph/-/blob/0aa540ecabb597a41fa4fbbe939391da80120691/rust/src/java_compat/bit_vector.rs (and test case)

It depends on my mmap wrapper because it needs to be able to add an offset that does not align with memory pages.