Improve how we detect whether an NPM install is necessary

[sodic]

Note

Look into #1838 first.

See this todo for context:

wasp/waspc/src/Wasp/Generator/NpmInstall.hs

Line 160 in e4932ec

-- TODO(martin): Here, we do a single check for all the deps. This means we don't know if user deps

[Martinsos]

This might be connected to the idea that @infomiho suggested, which is using npm workspaces. In that case, the whole installation step might become simpler / different, so we will probably want to first look into npm workspaces and only then into this.