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_compound_global/case.ww

@@ -0,0 +1,11 @@
+//ww:run-exit 2
+// Migrated from 700_e2e row 120.
+package main;
+let G: f64 = 10.0;
+fn main() i32 = {
+  G += 5.0;
+  G *= 2.0;
+  G -= 20.0;
+  G /= 5.0;
+  return G: i32;
+};