Add N_PRESERVE_COREPACK

[shadowspawn]

Pull Request

Problem

The --preserve and N_PRESERVE_NPM features just cover npm (and npx) but not corepack. Users may wish to preserve corepack as well.

See: #735

Solution

It seems reasonable for --preserve to preserve corepack too.

corepack is distributed as an npm package, but it is not part of npm as such. Add a separate environment variable rather than lump it under the existing one.

• have --preserve cover corepack as well
• add N_PRESERVE_COREPACK (rather than include corepack in N_PRESERVE_NPM)

ChangeLog

• also preserve corepack when use --preserve
• add environment variable for N_PRESERVE_COREPACK