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_slice_from_array/case.ww

@@ -0,0 +1,13 @@
+//ww:run-exit 60
+// Migrated from 700_e2e row 16.
+package main;
+fn main() i32 = {
+  let arr: [4]u8;
+  arr[0] = 10: u8; arr[1] = 20: u8;
+  arr[2] = 30: u8; arr[3] = 99: u8;
+  let s: []u8 = arr[0:3];
+  let sum: i32 = 0;
+  let i: i32 = 0;
+  for (i < s.len) { sum += s[i]: i32; i += 1; };
+  return sum;
+};