(WON'T FIX) Don't Interwine Bit and Byte Aligned Operations in BitReader

[tustvold]

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

BitReader contains a mixture of byte-aligned APIs such as get_aligned and get_vlq_int along with bit-aligned APIs such as get_value and get_batch. This makes the implementation kind of hard to follow, there is a buffer but this is only used for bit-level APIs, there is a bit_offset, but this is not used for some APIs, etc...

Describe the solution you'd like

Explicitly split the implementation of aligned APIs that operate on the byte stream from unaligned APIs that operate on the bit stream.

Describe alternatives you've considered

The current code is not incorrect and could remain unchanged