test(e2e): match API/toolchain location

The end-to-end tests now use the same folder structure as the targets they're testing under //labgrid.

Before:

e2e/
├─ docker/
├─ localhost/
├─ python/
├─ qemu/
├─ toolchain/
│  ├─ config/

After:

e2e/
├─ binary/
├─ flag/
│  ├─ device/
├─ genrule/
├─ run/
│  ├─ binary/
├─ test/
├─ toolchain/
│  ├─ config/
│  │  ├─ qemu/
examples/
├─ docker/
│  ├─ python/

Closes #34 (closed).