$SNAPCRAFT_PROJECT_NAME used in a remote part expands to wrong value

[Lucy Llewellyn]

In my alsa remote part I've attempted to use $SNAPCRAFT_PROJECT_NAME to build a path to the final snap installation directory expecting it to expand to the name of the consuming snapcraft.yaml. Instead it expands to `alsa` because that's the name on the snapcraft.yaml containing the remote part. This is counter-intuitive; I expect $SNAPCRAFT_PROJECT_NAME to always be the project that snapcraft started building - i.e. the consumer of the remote part, and not the name of any remote parts included as a dependency.