feat(config): cli.packageManager override support

[rigor789]

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What is the current behavior?

A globally set package manager is used (ns package-manager set npm|yarn|pnpm) and has to be switched globally when switching between projects that use different package managers.

What is the new behavior?

Projects can now set the packageManager in the nativescript.config.ts at cli.packageManager

Quickest way is to use ns config set cli.packageManager yarn to update the config.

Implements #5595