[SveEmitter] Add IsAppendSVALL and builtins for svptrue and svcnt[bhwd]

Some ACLE builtins leave out the argument to specify the predicate
pattern, which is expected to be expanded to an SV_ALL pattern.

This patch adds the flag IsAppendSVALL to append SV_ALL as the final
operand.

Reviewers: SjoerdMeijer, efriedma, rovka, rengolin

Reviewed By: efriedma

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77597