devel/llvm-{cheri,cheriot,morello}: new snapshots
Major changes:
llvm-cheri: merge LLVM 15
llvm-cheriot: switch the fork at github.com/CHERIoT-Platform
llvm-morello: merge LLVM 14
Rework patching and filtering of commands and man pages to better
accomdate version skew between the different ports now that all three
have different bases.
Centralize the addition of ${.CURDIR}/files to EXTRA_PATCHS.
llvm-{cheri,morello}: don't install std*.h
As with regular llvm ports, don't install std*.h as they conflict with
FreeBSD versions.
While here, update llvm-cheri to the latest snapshot.