test: consolidate Go tests (#39962)

Consolidate all Go tests. Coverage is identical to before. Go tests are
around 5% faster while being 7% smaller. No non-test code is touched.

tests/integration/api_packages_pub_test.go

@@ -117,19 +117,19 @@ description: ` + packageDescription,
 		uploadFile(t, result.URL, buildPackage(packageVersionLatest), http.StatusNoContent)
 	})
 
+	type VersionMetadata struct {
+		Version    string    `json:"version"`
+		ArchiveURL string    `json:"archive_url"`
+		Published  time.Time `json:"published"`
+		Pubspec    any       `json:"pubspec,omitempty"`
+	}
+
 	t.Run("Download", func(t *testing.T) {
 		defer tests.PrintCurrentTest(t)()
 
 		req := NewRequest(t, "GET", fmt.Sprintf("%s/api/packages/%s/%s", root, packageName, packageVersion))
 		resp := MakeRequest(t, req, http.StatusOK)
 
-		type VersionMetadata struct {
-			Version    string    `json:"version"`
-			ArchiveURL string    `json:"archive_url"`
-			Published  time.Time `json:"published"`
-			Pubspec    any       `json:"pubspec,omitempty"`
-		}
-
 		result := DecodeJSON(t, resp, &VersionMetadata{})
 
 		assert.Equal(t, packageVersion, result.Version)
@@ -147,13 +147,6 @@ description: ` + packageDescription,
 		req := NewRequest(t, "GET", fmt.Sprintf("%s/api/packages/%s", root, packageName))
 		resp := MakeRequest(t, req, http.StatusOK)
 
-		type VersionMetadata struct {
-			Version    string    `json:"version"`
-			ArchiveURL string    `json:"archive_url"`
-			Published  time.Time `json:"published"`
-			Pubspec    any       `json:"pubspec,omitempty"`
-		}
-
 		type PackageVersions struct {
 			Name     string             `json:"name"`
 			Latest   *VersionMetadata   `json:"latest"`