Manual sweep: Custom vertex MET with CA

This is a manual sweep for !54716 (merged), which added support for custom vertex MET in the ComponentAccumulator-based config in master. The automatic sweep failed because it included some changes to derivation code which doesn't exist in 22.0. Those changes have been removed here.

Reconstruction output should be unaffected; this is mainly just relevant for derivations. The main motivation for sweeping this into 22.0 at all is to keep the MET config in sync with master such that future sweeps are easier to deal with.