Goals are to simplify code, improve test coverage, and clean up tech debt.
Subcomponents of the task are:
[ ] Add flags to their appropriate categories, such as mandatory flags, or standard flags.
[x] Add CHECKDATASIG to standard flags.
[ ] Add DER to mandatory flags.
[ ] DER seems to be eclipsed by STRICTENC, can probably be removed?
[ ] Add SIGPUSHONLY to mandatory flags.
[ ] Add CLEANSTACK to mandatory flags.
[x] Delete the STANDARD+CDS group of flags as CDS should be standard.
[ ] Convert activation tests to feature tests.
[x] Change logic of SCRIPT_ALLOW_SEGWIT_RECOVERY flag from "permissive" to "restrictive" (SCRIPT_DISALLOW_SEGWIT_RECOVERY).
[x] Remove or simplify Segwit Recovery activation.
[x] Add "SCRIPT_DISALLOW_SEGWIT_RECOVERY" to standard flags.
[ ] Remove Schnorr activation, make it "always on". Remove SCRIPT_ENABLE_SCHNORR flag.
[ ] Remove GreatWall activation.