Compatibility with `nx affected` for test / build executors

[AgentEnder]

Current behavior

The current setup fails when running the following:

• nx run {my-app}:build
• nx affected:build
• nx affected --target build

Expected Behavior

The above succeed.

Notes

This is partially due to the setup of ios / android targets that pull config from the actual build target, which does not work on its own. This target should be made to work (possibly by invoking a webpack-only build), and then the ios / android targets could invoke it.

If the ios / android targets could consume a webpack-only build, then their executor could use targetDependencies to require the regular build target be hit first, and not have to do a separate webpack build for android and ios.

[NathanWalker]

Noting here to also include a generator to add the {N} unit test runner with proper test target which would also work with affected.