[SveEmitter] Add builtins for svmov_b and svnot_b.

These are custom expanded in CGBuiltin:

  svmov_b_z(pg, op) <=> svand_b_z(pg, op, op)
  svnot_b_z(pg, op) <=> sveor_b_z(pg, op, pg)

Reviewers: SjoerdMeijer, efriedma, ctetreau, rengolin

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D79039