chore: Strip noisy metadata from patches

Issue: Strip metadata from patches in `dev-save-patches` (#45 - closed)

Description

Closes Strip metadata from patches in `dev-save-patches` (#45 - closed) by:

• Stripping out the top-line metadata which is mostly arbitrary except the commit message.
• Setting --no-signature so that the environment specific git version isn't written to the patch.

This MR also:

• Adds a small check to warn the user if they ran dev-save-patches.sh on an empty changeset.
• Changes how we handle the $patches_dir_backup. Instead of creating a backup and working off of the $patches_dir, we create a .tmp directory and work off that. We finally move it all over to $patches_dir if things are good.

How to test?

Locally:

1. Checkout this MR changes
2. Run cd vscode to enter the vscode submodule.
3. Run git reset --hard $(../scripts/dev-vscode-target-sha.sh) to reset your submodule to the base version.
4. Run ../scripts/dev-apply-patches.sh
5. Run ../scripts/dev-save-patches.sh
6. There should be no changes to the patch files 🎉