Add support for multiple code directories

**What would you like to be added**:
Today we support adding a single code directory with sha256 hashes of each page in the binary. By default the `codesign` utility attaches two code directories, one for sha256 hashes and another one for sha1 hashes.

**Why is this needed**:
This can help with backwards compatibility for older macs (more details needed).

Start with the existing single-code-directory signing path and compare its behavior with the codesign utility, which attaches SHA-256 and SHA-1 code directories. Done means a binary can carry both directories while preserving the current SHA-256 behavior and supporting older Macs.

Written by the indexing model from the issue text.