test: migrate 700_e2e rows to corpus fixtures; retire the carrier

136 rows migrated, 0 already owned, 3 wwstage-failing rows held out.

test/wcc/data/r700_f64_cmp/case.ww

@@ -0,0 +1,9 @@
+//ww:run-exit 7
+// Migrated from 700_e2e row 8.
+package main;
+fn main() i32 = {
+  let a: f64 = 1.5;
+  let b: f64 = 2.5;
+  if (a < b) { if (b > a) { return 7; }; };
+  return 0;
+};