Reconsider representation for flags

[blaesus]

For bitvec in Mongo ops (such as response_flags in OP_REPLY, using them as i32/u32 is cumbersome and error-prone (one needs to use bit manipulation to extract information).

Rust provides BitVec.

Alternatively, we might as well just parse the initial bytes as struct { fieldA: bool, fieldB: bool } and only handle bitvec logic in seralizer and parser.

cc @poppindouble

[poppindouble]

I do agree with you, the i32/u32 representation is not a good option, since this field is not representing a i32/u32 number, Bit 0, 1, 16 have their own meaning,

However the BitVec has been removed from standard collections, you can check the PR here. The link above might not be what we want.

I also checked other two crate which allows you interact with bit more easily in Rust:

1. https://crates.io/crates/bit-vec
2. https://crates.io/crates/bitvec

Those two crates might not be trustable, they either don't have enough maintain resources or they don't have a strong evidence it is a trustable crates.

[blaesus]

Superseded by #51