Investigate how Integer Arithmetic is supported in CKKS pipeline

In CKKS pipeline, aside from handling `arith.{add,mul}f`, we also have some code handling `arith.{add,mul}i` in like `secret-insert-mgmt-ckks` and `secret-to-ckks`. Technically we can support some kind of integer arithmetic in CKKS, however, we have no example mlir that goes through them to actually test them.

This issue is intended as meta-issue on integer arithmetic support in CKKS.

One sub issue is the `arith.uitofp` one (#1628)