Fix unsteady progress when installing updates

[zorgiepoo]

We move showing installing the update after showing that the update is ready to install. We also fix progress status in dmg unarchiver not reaching 100% in some cases.

We deprecate a couple of user driver methods and replace/combine them with a method that shows installing the update and lets the driver know if the target is terminated.

Fixes #2068

Misc Checklist:

• My change requires a documentation update on Sparkle's website repository
• My change requires changes to generate_appcast, generate_keys, or sign_update

Only bug fixes to regressions or security fixes are being backported to the 1.x (master) branch now. If you believe your change is significant enough to backport, please also create a separate pull request against the master branch.

Testing

I tested and verified my change by using one or multiple of these methods:

• Sparkle Test App
• Unit Tests
• My own app
• Other (please specify)

Tested sparkle-cli installing another app that is running or already terminated, tested an app updating itself.

macOS version tested: 12.1 (21C52)