expose known_number_bytes and parser methods for bytes -> number

[davidhewitt]

This exposes known_number_bytes, which matches known_float, known_str signatures etc, so should not be controversial.

I also exposed three helper methods to parse the subsequent byte range.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[codspeed-hq]

Merging this PR will not alter performance

✅ 70 untouched benchmarks

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_{Comparing dh/known-number-bytes (0bb223a) with main (dcdc93d)}

[samuelcolvin]

Lgtm