Sliceable BitMap

[tustvold]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

Currently BitMap is a simple wrapper around a Buffer. This limits it to slicing on multiples of 8, as Buffer can only slice at byte boundaries.

Describe the solution you'd like

Add an offset and length to BitMap, updating the accessors to take this into account. This may require deprecating and removing buffer_ref, and/or making it panic if non-zero offset.

Add a slice method to BitMap that uses the offset and length to perform zero-copy slicing.

Describe alternatives you've considered

We could not do this.

Additional context

Feeds into #1799

[HaoYang670]

Related to this issue: #1728