serialized_length_from_bytes()

[arvidn]

This PR adds an implementation of serialized_length_from_bytes() where any back-references are validated. Rename the existing function to indicate that the input is trusted (i.e. not fully validated).

In support of this, it also adds:

• a fuzzer ensuring that any buffer that's accepted by serialized_length_from_bytes() also parses correctly
• a benchmark comparing parsing with- and without back-references, computing the serialized length with and without validation

objective

The objective is to ensure that the buffer is a valid serialization if it passes this function. That way, an invalid CLVM program fails early, at parse-time, rather than time-of-use. Currently, the Program class in chia_rs (the counterpart to SerializedProgram) is parsed in a relaxed manner, and so might fail later, in run().

This can also tie into trusted- and untrusted parsing of Streamable. So trusted programs don't need to be validated to the same extent.

benchmarks:

     Running benches/deserialize.rs (target/release/deps/deserialize-2f84100aeab5fe87)
deserialize/serialized_length_from_bytes
                        time:   [150.42 µs 150.99 µs 151.54 µs]
deserialize/serialized_length_from_bytes_trusted
                        time:   [44.187 µs 44.339 µs 44.522 µs]
Found 1 outliers among 10 measurements (10.00%)
  1 (10.00%) high mild
deserialize/node_from_bytes_backrefs
                        time:   [239.17 µs 240.30 µs 241.73 µs]
Found 1 outliers among 10 measurements (10.00%)
  1 (10.00%) high mild
deserialize/node_from_bytes
                        time:   [222.05 µs 222.99 µs 223.73 µs]
Found 1 outliers among 10 measurements (10.00%)
  1 (10.00%) low severe

[coveralls-official]

Pull Request Test Coverage Report for Build 7261386983

• 119 of 122 (97.54%) changed or added relevant lines in 1 file are covered.
• 4 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.03%) to 93.804%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/serde/tools.rs	119	122	97.54%

Files with Coverage Reduction	New Missed Lines	%
src/serde/tools.rs	4	97.18%

Totals
Change from base Build 7261384226:	0.03%
Covered Lines:	5405
Relevant Lines:	5762

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💛 - Coveralls

[richardkiss]

Seems okay.