cranelift: Implement nan canonicalization for vectors (#3146)

This fixes some fuzz bugs that came about enabling simd where nan
canonicalization is performed on the fuzzers but cranelift would panic
on these ops for vectors. This adds some custom codegen with `bitselect`
to ensure any nan lanes are canonical-nan lanes in the canonicalized
operations.

tests/all/wast.rs

@@ -40,6 +40,10 @@ fn run_wast(wast: &str, strategy: Strategy, pooling: bool) -> anyhow::Result<()>
         .strategy(strategy)?
         .cranelift_debug_verifier(true);
 
+    if wast.ends_with("canonicalize-nan.wast") {
+        cfg.cranelift_nan_canonicalization(true);
+    }
+
     // By default we'll allocate huge chunks (6gb) of the address space for each
     // linear memory. This is typically fine but when we emulate tests with QEMU
     // it turns out that it causes memory usage to balloon massively. Leave a