switch from proxyquire to @node-loaders/mock

[mshima]

@node-loaders/mock provides esm and commonjs modules mocking support.
This will make the cli transition to esm easier due to existing module mocking usage.

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[Tcharl]

I'm not so happy to use jhipster contributors' third party lib as a dependency: I would either prefer to find another alternative (i.e. testdouble) or either embed it in jhipster's monorepo to get maintained by us.
Relying on a one-man-maintained library (without any community behind it), no matter how brilliant the contributor is is usually a very bad idea.
My advice would be to revert this one until there are more contributors on @mshima libs (node-loaders/mock, ...) or a pretty big usage (1K+ like) and to rely on more solid community-provided libs in the meantime (for example finishing https://github.com/jhipster/generator-jhipster/pull/20500/files)