Add the functionality to lower SVE rounding operations for passthru variant.
Created a new test case file for all rounding operations.
So we can prove the DAGCombine for these intrinsics is the canonical route, can you please change this and the following sve_frint instances to null_frag. Once FRECPX and FSQRT follow a similar path we'll remove the parameter.
Since there's no expected variance for these tests can you use update_llc_test_checks.py to generate the check lines. It'll just make it easier in the future if somebody adds anything new.