Use stdlib fallible alllocation primitives

[baumanj]

Rust 1.57 stabilized stdlib fallible allocation, so it would be beneficial to replace the relevant code in this crate to use the stdlib where possible. I still think there's a lot of value in the distinct fallible collection types, however, since the stdlib collections require calling the fallible reserve functions appropriately to avoid infallible allocations.

[kornelski]

Done in #24

[baumanj]

Awesome! Thanks @kornelski