feat: add limited support for devEngines and .corepack.env

[aduh95]

This PR introduces the concept of .corepack.env which would allow project maintainers to customize some parts of Corepack. We realistically cannot release it until Node.js 18.x is EOL (env parser is only available on Node.js 20.x LTS and later) in April, EDIT: actually it won't be as big of a deal as I thought, it falls back elegantly when run on a Node.js version without .env support.

devEngines support in this PR is limited to packageManager only, only one packageManager can be specified, the onFail field is ignored.
This PR also does not add support of devEngines to corepack use and corepack up, which should be addressed before releasing. EDIT: this has been addressed

Fixes: #567
Fixes: #402
Fixes: #95

Should unblock fixing: #628

[styfle]

Can we separate into two PRs since this sounds like two separate features?

• add support for devEngines
• add support for .corepack.env

This way we don't block the devEngines feature on account of any bikesheding that could come from .corepack.env

[GeoffreyBooth]

devEngines support in this PR is limited to packageManager only, only one packageManager can be specified, the onFail field is ignored.

Can you please explain these limitations?