Tests should use different output directory as to not troll the library author

[NullVoxPopuli]

dist is currently very overloaded.

This could lead to things like:

• accidentally publishing the test-app to npm instead of the rollup's dist output (depends on which order you run things)
• accidentally thinking self-imports work without a resolve.alias config (which we do have now, but slightly beside the point)

We want it to be possible to:

• pnpm build
• pnpm test:ember
• pnpm publish

and have the correct dist directory be published.

This may beg the question:

• do we use dist-types instead of declarations? idk 🤷 disco for outside this PR