fix(ci): Fix macOS build

[rajivshah3]

Summary

• Installs Python 2 on macOS by downloading the PKG from python.org. This is necessary because actions/setup-python has removed support for Python 2 (python2.7 will be removed from the python-versions on June 19 actions/setup-python#672) but we still need it for the DMG builder script in electron-builder. This needs to be run right before building the DMG since Python 3 is necessary for node-gyp when building the bindings, but the Python 2 installation script will override it.
• Remove NODE_GYP_FORCE_PYTHON
• Use macOS 13 runner with latest stable Xcode
• Set macOS deployment target to 10.13
• Patch librocksdb-sys to support macOS 10.13 (see fix: support macOS 10.13 iota-sdk#195)

Changelog

- Drop support for macOS 10.12 (all models that support macOS 10.12 also support macOS 10.13)

Testing

CI passes

Platforms

Please select any platforms where your changes have been tested.

• Desktop
  • MacOS
  • Linux
  • Windows
• Mobile
  • iOS
  • Android

Instructions

Please describe the specific instructions, configurations, and/or test cases necessary to test and verify that your changes work as intended.

...

Checklist

Please tick the following boxes that are relevant to your changes.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or modified tests that prove my changes work as intended
• I have verified that new and existing unit tests pass locally with my changes
• I have verified that my latest changes pass CI workflows for testing and linting
• I have made corresponding changes to the documentation

[rajivshah3]

Closing in favor of #7303