Fix IsKnownNonNull assert for SIMD base addresses (#129788)

Fixes #129738.

I added this assert in #129447,
but it turns out we can visit that functions for SIMD values as
addresses (e.g. via `fgValueNumberIndirNullCheckExceptions` calls it
with a SIMD base address (SVE gather/scatter).

---------

Co-authored-by: EgorBo <egorbo@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: EgorBo

src/coreclr/jit/valuenum.cpp

@@ -1619,7 +1619,13 @@ bool ValueNumStore::IsKnownNonNull(ValueNum vn)
         return false;
     }
 
-    assert((TypeOfVN(vn) == TYP_I_IMPL) || (TypeOfVN(vn) == TYP_REF) || (TypeOfVN(vn) == TYP_BYREF));
+    // Ignore corner cases like a SIMD value - SIMD could be a base address of an indirection
+    // (e.g. SVE GatherVector, a vector of addresses).
+    var_types vnType = TypeOfVN(vn);
+    if ((vnType != TYP_I_IMPL) && (vnType != TYP_REF) && (vnType != TYP_BYREF))
+    {
+        return false;
+    }
 
     target_ssize_t offset;
     PeelOffsets(&vn, &offset);