Don't write into node_modules by default

[kylecordes]

Currently, ng build and possibly other commands write into the node modules directory.

A recently added change #15900 has created the ability to configure CLI to not do this. Which is good, but not great.

This is a feature request to make CLI, by default, not write to the node modules directory (other than in ng update of course). Perhaps it could default a cache directory next to angular.json, or a temp directory, or elsewhere. Regardless, such a change would clarify that a build operation takes node_modules as pure input, not as a scratch, temp, or output location.

[alan-agius4]

Closed via #21827