[SveEmitter] Add range checks for immediates and predicate patterns.

[SveEmitter] Add range checks for immediates and predicate patterns.

Summary:
This patch adds a mechanism to easily add range checks for a builtin's
immediate operands. This patch is tested with the qdech intrinsic, which takes
both an enum for the predicate pattern, as well as an immediate for the
multiplier.

Reviewers: efriedma, SjoerdMeijer, rovka

Reviewed By: efriedma, SjoerdMeijer

Subscribers: mgorny, tschuett, mgrang, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D76678