[Enhancement] Improve the parser performances

[arcanis]

Context

We parse the lockfiles using a format managed by the @berry/parsers package (we call it syml, for Simpler Yaml). The idea was that since we didn't need the whole power of yaml, a smaller parser should theoretically be faster.

Well, as it turns out, it's not so simple. Our current parsing time (based on a peg.js-generated parser) is ~180ms for the Berry lockfile. In contrast, using js-yaml brought the parsing time to ~60ms.

It's very likely that I made the peg grammar non-optimal, so if someone wants to take a shot at optimizing it (or rewriting it with another tool like chevrotain, for example) it would be helpful. If we can't make it faster, I guess we'll switch to js-yaml.

Describe alternatives you've considered

We could also switch to js-yaml without looking back. That would be ok for me, but we will first have to check how much it adds/removes to the bundle size. Note that if we do that we'll still need to keep the peg parser in our tree as a fallback at least until the 3.0 (otherwise we wouldn't be able to support old-style lockfiles, which would be bad for the migration story).

[arcanis]

Implemented in #183