[SveEmitter] Implement builtins for contiguous loads/stores

This adds builtins for all contiguous loads/stores, including
non-temporal, first-faulting and non-faulting.

Reviewers: efriedma, SjoerdMeijer

Reviewed By: SjoerdMeijer

Tags: #clang

Differential Revision: https://reviews.llvm.org/D76238