[CIR] Add support for nontemporal loads and stores (llvm#1494)

This PR adds a new boolean flag to the `cir.load` and the `cir.store`
operation that distinguishes nontemporal loads and stores. Besides, this
PR also adds support for the `__builtin_nontemporal_load` and the
`__builtin_nontemporal_store` intrinsic function.

Author: Lancern