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_os_write/case.ww

@@ -0,0 +1,5 @@
+//ww:run-exit 3
+// Migrated from 700_e2e row 17.
+package main;
+import os;
+fn main() i32 = { return os.write(1, "ok\n".ptr, 3): i32; };