refactor(proto): Extract protobuf dependency management

In order to use a managed dependency in the `protoc` configuration settings, dependencyResolutionManagement must be used instead of enforcePlatform.

kork-proto/kork-proto.gradle

@@ -1,18 +1,16 @@
 plugins {
-  id "java-library"
-  id "com.google.protobuf" version "0.8.12"
+  alias libs.plugins.protobuf
 }
 
 dependencies {
   api(platform(project(":spinnaker-dependencies")))
 
-  implementation "com.google.protobuf:protobuf-java"
+  implementation libs.protobuf.java
 }
 
 protobuf {
   protoc {
-    // TODO: figure out how to reference version in BOM.
-    artifact = "com.google.protobuf:protoc:3.21.12"
+    artifact = libs.protoc.get()
   }
 }
 

settings.gradle

@@ -14,6 +14,19 @@
  * limitations under the License.
  */
 
+dependencyResolutionManagement {
+  versionCatalogs {
+    libs {
+      version('protobuf', '3.25.2')
+
+      library('protobuf-java', 'com.google.protobuf', 'protobuf-java').versionRef('protobuf')
+      library('protoc', 'com.google.protobuf', 'protoc').versionRef('protobuf')
+
+      plugin('protobuf', 'com.google.protobuf').version('0.9.4')
+    }
+  }
+}
+
 if (spinnakerGradleVersion.endsWith('-SNAPSHOT')) {
   pluginManagement {
     repositories {