[build] Restructure to composite build

conventions/src/main/kotlin/de.siphalor.tweed5.test-utils.gradle.kts

@@ -0,0 +1,21 @@
+plugins {
+	java
+	alias(libs.plugins.lombok)
+}
+
+dependencies {
+	implementation(project(":tweed5-serde-api"))
+	implementation(platform(libs.junit.platform))
+	implementation(libs.junit.core)
+	implementation(libs.mockito)
+	implementation(libs.assertj)
+}
+
+lombok {
+	version = libs.versions.lombok.get()
+}
+
+java {
+	sourceCompatibility = JavaVersion.toVersion(libs.versions.java.test.get())
+	targetCompatibility = JavaVersion.toVersion(libs.versions.java.test.get())
+}