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_syscall_write/case.ww

@@ -0,0 +1,6 @@
+//ww:run-exit 13
+// Migrated from 700_e2e row 11.
+package main;
+@symbol("rt_syscall") fn rt_syscall(num: i64, a: i64, b: i64, c: i64) i64;
+fn print(s: str) i64 = { return rt_syscall(1, 1, s.ptr: i64, s.len: i64); };
+fn main() i32 = { return print("hello, world\n"): i32; };