In real services most of our time ends up in the `Read1()` function,
which populates one byte into the bit buffer.
Change this to read in as many as possible bytes at a time into that
buffer.
Additionally, generate all possible (to some depth) parser geometries,
and add a benchmark for them. Run that benchmark and select the best
geometry for decoding base64 strings (since this is the main use-case).
(gives about a 30% speed boost parsing base64 then huffman encoded
random binary strings)
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Co-authored-by: ctiller <ctiller@users.noreply.github.com>
Craig Tiller