feat: use isproj-only project files and local settings

Closes #6

src/crates/package-infra/tests/workflow.rs

@@ -18,7 +18,7 @@ fn png(path: &Path, size: u32) {
 }
 fn fixture() -> (tempfile::TempDir, PathBuf) {
     let temp = tempfile::tempdir().unwrap();
-    let path = temp.path().join("package-project.json");
+    let path = temp.path().join("InstallerProject.isproj");
     let mut doc = infra::create_project(&path).unwrap();
     let payload = temp.path().join("payload");
     fs::create_dir_all(payload.join("Assets")).unwrap();