Rollup merge of #121376 - Nadrieril:mir-half-ranges, r=pnkfelix

Skip unnecessary comparison with half-open range patterns

This is the last remaining detail in the implementation of half-open range patterns. Until now, a half-open range pattern like `10..` was converted to `10..T::MAX` before lowering to MIR, which generated an extra pointless comparison. With this PR we don't generate it.

Author: GuillaumeGomez