rename some wiggle tests to reflect new witx ast names

arrays are now lists
structs are now records
unions are now variants

this ruins some of my union puns, oh well

crates/wiggle/tests/variant.witx

@@ -0,0 +1,27 @@
+(use "errno.witx")
+(use "excuse.witx")
+
+(typename $reason
+  (variant (@witx tag $excuse)
+    (case $dog_ate f32)
+    (case $traffic s32)
+    (case $sleeping)))
+
+(typename $reason_mut
+  (variant (@witx tag $excuse)
+    (case $dog_ate (@witx pointer f32))
+    (case $traffic (@witx pointer s32))
+    (case $sleeping)))
+
+(module $variant_example
+  (@interface func (export "get_tag")
+    (param $r $reason)
+    (result $error (expected $excuse (error $errno)))
+  )
+
+  (@interface func (export "reason_mult")
+    (param $r $reason_mut)
+    (param $multiply_by u32)
+    (result $error (expected (error $errno)))
+  )
+)