gradle: Improve compatibility with Gradle 8

all/build.gradle

@@ -52,19 +52,12 @@ tasks.named("javadoc").configure {
     }
 }
 
-tasks.register("jacocoMerge", JacocoMerge) {
+tasks.named("jacocoTestReport").configure {
     dependsOn(subprojects.jacocoTestReport.dependsOn)
     dependsOn(project(':grpc-interop-testing').jacocoTestReport.dependsOn)
-    mustRunAfter(subprojects.jacocoTestReport.mustRunAfter)
-    mustRunAfter(project(':grpc-interop-testing').jacocoTestReport.mustRunAfter)
-    destinationFile = file("${buildDir}/jacoco/test.exec")
-    executionData = files(subprojects.jacocoTestReport.executionData)
+    executionData.from files(subprojects.jacocoTestReport.executionData)
             .plus(project(':grpc-interop-testing').jacocoTestReport.executionData)
             .filter { f -> f.exists() }
-}
-
-tasks.named("jacocoTestReport").configure {
-    dependsOn(jacocoMerge)
     reports {
         xml.required = true
         html.required = true

authz/build.gradle

@@ -32,11 +32,11 @@ dependencies {
 }
 
 tasks.named("jar").configure {
-    classifier = 'original'
+    archiveClassifier = 'original'
 }
 
 tasks.named("shadowJar").configure {
-    classifier = null
+    archiveClassifier = null
     dependencies {
         exclude(dependency {true})
     }

build.gradle

@@ -453,7 +453,7 @@ subprojects {
         tasks.register("japicmp", me.champeau.gradle.japicmp.JapicmpTask) {
             dependsOn jar
             oldClasspath = files(baselineArtifact)
-            newClasspath = files(jar.archivePath)
+            newClasspath = files(jar.archiveFile)
             onlyBinaryIncompatibleModified = false
             // Be quiet about things that did not change
             onlyModified = true