Migrate to the Struct API and output via bullet_stream

[schneems]

This PR deprecates the commons::build_output module in favor of the bullet stream crate. It also uses the updated "struct API" from libcnb.rs. To minimize the change, I tried to avoid refactoring code as much as possible.

Future refactors (not implemented)

I would like to eventually move the layers/*.rs files out and get rid of that nested directory. It adds nothing but overhead. I would also like to refactor the enum based approach to layer invalidation. It's overly complex and adds little value. Ideally I would like a list of all keys that changed and I experimented with a way to do this automatically via relying on toml comparisons in #203. I think this can be extracted and generalized.

[runesoerensen]

This PR would be faster to review if it introduced the changes in at least 2 PRs instead:

1. Migrate to struct layer API.
2. Migrate to bullet_stream.
3. Handles deprecations in the commons/publicly shared crate (although this could also be done in 2, as it doesn't really have an impact on the review complexity like the other changes do).

[runesoerensen]

Might make sense to combine the two match layer.state blocks?

Suggested change

	match layer.state {
	LayerState::Restored { .. } => {
	bullet = bullet.sub_bullet("Using cached Ruby version");
	}
	LayerState::Empty {
	cause:
	EmptyLayerCause::InvalidMetadataAction { ref cause }
	| EmptyLayerCause::RestoredLayerAction { ref cause },
	} => {
	bullet = bullet.sub_bullet(format!("Clearing cache ({cause})"));
	}
	LayerState::Empty {
	cause: EmptyLayerCause::NewlyCreated,
	} => {}
	};
	match layer.state {
	LayerState::Restored { .. } => {}
	LayerState::Empty { .. } => {
	let timer = bullet.start_timer("Installing");
	let tmp_ruby_tgz = NamedTempFile::new()
	.map_err(RubyInstallError::CouldNotCreateDestinationFile)
	.map_err(RubyBuildpackError::RubyInstallError)?;
	let url = download_url(&new_metadata.target_id(), &new_metadata.ruby_version)
	.map_err(RubyBuildpackError::RubyInstallError)?;
	download(url.as_ref(), tmp_ruby_tgz.path())
	.map_err(RubyBuildpackError::RubyInstallError)?;
	untar(tmp_ruby_tgz.path(), layer.path())
	.map_err(RubyBuildpackError::RubyInstallError)?;
	layer.write_metadata(new_metadata)?;
	bullet = timer.done();
	}
	};
	match layer.state {
	LayerState::Restored { .. } => {
	bullet = bullet.sub_bullet("Using cached Ruby version");
	}
	LayerState::Empty { ref cause } => {
	match cause {
	EmptyLayerCause::InvalidMetadataAction { cause }
	| EmptyLayerCause::RestoredLayerAction { cause } => {
	bullet = bullet.sub_bullet(format!("Clearing cache ({cause})"));
	}
	EmptyLayerCause::NewlyCreated => {}
	};
	let timer = bullet.start_timer("Installing");
	let tmp_ruby_tgz = NamedTempFile::new()
	.map_err(RubyInstallError::CouldNotCreateDestinationFile)
	.map_err(RubyBuildpackError::RubyInstallError)?;
	let url = download_url(&new_metadata.target_id(), &new_metadata.ruby_version)
	.map_err(RubyBuildpackError::RubyInstallError)?;
	download(url.as_ref(), tmp_ruby_tgz.path())
	.map_err(RubyBuildpackError::RubyInstallError)?;
	untar(tmp_ruby_tgz.path(), layer.path())
	.map_err(RubyBuildpackError::RubyInstallError)?;
	layer.write_metadata(new_metadata)?;
	bullet = timer.done();
	}
	};

[runesoerensen]

This doesn't handle the cases when the metrics agent is updated due to either another metrics agent URL, or invalid metadata (the original code logged these events)