[Perf] Avoid allocations in the Sanitizer

[ljedrz]

The Sanitizer is used very prominently in our parsing functions, and it is also a source of many allocations, most of which are temporary. Similarly to #5, it is possible to avoid using some of the expensive parsing functions, though in this case we need to apply some heuristics.

The perf improvements are quite large, and I've measured them both with a 15-minute run of a --dev node and using hyperfine on a small binary that parsed all the valid .aleo programs currently present in the snarkVM codebase.

dev node:

• all allocs are down ~15%, of which almost all are temporary
• in Program::from_str specifically, allocs are reduced by ~64%, of which temp allocs ~88%

parsing all .aleo programs using Program::from_str:

• allocs are reduced by ~41%
• growth reallocs are down ~70%
• runtime is reduced by ~31%

Update: I crunched the parsing figures again using Program::from_str (as opposed to just Sanitizer::parse), which provides a better bigger picture.

[vicsn]

@d0cd