Test for and correct invalid assertion in Inject.method docs
I am not exactly sure where I got the idea from that only one method is picked, however at first glance the assertion is completely incorrect and as such has been corrected to the actual (observed) behaviour.
This change has been prompted by inspection of https://github.com/ModificationStation/StationAPI/blob/efa7519b1674e325c7c6c38257c3aa5b8e44493e/station-audio-loader-v0/src/main/java/net/modificationstation/stationapi/mixin/audio/BlockSoundGroupMixin.java#L21-L22 (commit: 877885d)
Also fix slices not including the last instruction within the slice. The way it is implemented is a hacky workaround, but likely well within the realm of "works".
Also implements a bunch of constant selectors and moved the constant selector implementations to their own package. (commit: 5186253)