Bump node required version and add ignore conflicting packages version.

[mshima]

Node 12.20.0 added stable esm module support.

• Many dependencies will depend on it eg: chore(deps): bump insight from 0.10.3 to 0.11.0 #15794.
• This allows to implement modular generator as mjs.
• It's a minor node version bump, may or may not be considered a breaking change, in jhipster I don't consider a breaking change since we always generate package.json with latest lts node version.

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