2c35a93b3c Generalize/simplify VectorReader into SpanReader (Pieter Wuille)
Pull request description:
Originally written for #21590 (safegcd-based MuHash inverses), but then found a better way that removed the need for it, so I'm submitting it independently.
ACKs for top commit:
MarcoFalke:
re-ACK 2c35a93b3c 🖨
shaavan:
ACK 2c35a93b3c
Tree-SHA512: 959e3251e0cfe20e13a50639b617c9dc2a561d613a0884d983c93d15dacb6d2305d760aa933d18ba055cef8a1651a344bcb6b3f93051ecf26d3f2efc5779efa4