spike: avoid keychain popups on macOS when 'but' accesses GUI keychain entries

[Byron]

Tasks

• identifier cleanup
• prep but for re-use in tauri
• make gitbutler-tauri a valid but executable
  • symlink the tauri executable instead (what about Windows though? It's not used there at all)
• validate on new nightly build
• remove extra binaries from distribution, but on non-windows only.
• validate distribution

[Byron]

@krlvi With the changes in this PR, I have made it so that neither but-testing nor but are included in the distribution, on all platforms. This also works on Windows which will need some love if people want to use the CLI anyway.

This will lead to a 75MB reduction in the installation size on MacOS, down to 100MB, and I will see how big the distributable is.

Please note that locally, we still build the but binary and symlink it as it's more convenient in dev mode, and the whole thing can be feature-toggled with Cargo. I hope to have more data later once the builds are finished.

[krlvi]

This is really cool. I wonder if this would make it easier to implement a but . functionality

[krlvi]

Btw - one thing to consider is we might need to update our brew setup (but can be installed that way too)