allow user to customize the installer terminal output

right now we have some stock output that happens when the installers are run. but often users like to print out branded messages, such as https://github.com/tursodatabase/turso-install/blob/main/install.sh#L31. it'd be cool to add:

- branded hello (printed when the installer starts)
- success (printed on success)
- failure (printed on error)

Start by tracing how cargo-dist generates and prints its installer output, then compare the branded message example in install.sh at line 31. The work is done when installer configuration can provide distinct start, success, and failure messages and each is emitted at the corresponding stage.

Written by the indexing model from the issue text.