Yarn 1.x: Investigate replacing pyarn with the native Yarn yarn.lock parser

[taylormadore]

In our initial implementation for the Yarn 1.x package manager in cachi2, we will use the pyarn library for parsing yarn.lock. Pyarn is a library that we maintain and there may be some benefit to use yarn itself instead to parse yarn.lock.

Here is Yarn's own parser: https://github.com/yarnpkg/yarn/tree/master/packages/lockfile
It is also distributed as a package in the npm registry, but caution that it has not been released for many years even though some changes have been made to the lockfile code in the repository.

Additional context from the discussion on the design: #585 (comment)