Eliminate simple_sds_sbwt types from the API

[jnalanko]

Replace simple_sds_sbwt::bit_vector::BitVector types in the public-facing API with bitvec::vec::BitVec. Keep using simple_sds_sbwt bit vectors internally when rank/select support is needed.

Why?

• bitvec types are more standard and thus more likely interoperable with user code.
• bitvec has a richer API and is easier to work with.

This may introduce some overhead when converting between bitvec::vec::BitVec to simple_sds_sbwt::bit_vector::BitVector, but I think there is probably some way to just re-interpret the raw data as the other kind of bit vector.

[jnalanko]

Work in progress at https://github.com/jnalanko/sbwt-rs-cli/tree/eliminate_simple_sds_from_api.

[jnalanko]

Mostly done in v0.4.2. Some dependencies remain at streaming_index.rs and sdsl_compatibility.rs.