Fix deprecations / be ready for Gradle 8.x

[pun-ky]

➜  gradle-aem-plugin git:(upgrades) ✗ gw
Using gradle at '/Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/gradlew' to run buildfile '/Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/build.gradle.kts':


> Task :compileKotlin
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/AemExtension.kt: (120, 30): 'getter for convention: Convention!' is deprecated. Deprecated in Java
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/bundle/BundlePlugin.kt: (18, 31): 'JavaPluginConvention' is deprecated. Deprecated in Java
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/bundle/BundlePlugin.kt: (44, 14): 'getter for convention: Convention!' is deprecated. Deprecated in Java
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/bundle/BundlePlugin.kt: (44, 35): 'JavaPluginConvention' is deprecated. Deprecated in Java
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/bundle/BundlePlugin.kt: (67, 53): 'getter for convention: Convention!' is deprecated. Deprecated in Java
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/bundle/BundlePlugin.kt: (75, 50): 'getter for convention: Convention!' is deprecated. Deprecated in Java
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/bundle/tasks/BundleJar.kt: (418, 35): 'getter for convention: Convention!' is deprecated. Deprecated in Java
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/common/cli/JarApp.kt: (34, 21): 'setter for main: String?' is deprecated. Deprecated in Java
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/common/instance/LocalInstance.kt: (277, 22): 'setter for main: String?' is deprecated. Deprecated in Java
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/common/instance/tail/InstanceAnalyzer.kt: (10, 2): This class can only be used with the compiler argument '-Xopt-in=kotlin.RequiresOptIn'
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/common/instance/tail/InstanceAnalyzer.kt: (34, 43): 'poll(): E?' is deprecated. Deprecated in the favour of 'tryReceive'. Please note that the provided replacement does not rethrow channel's close cause as 'poll' did, for the precise replacement please refer to the 'poll' documentation
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/common/instance/tail/LogNotifier.kt: (15, 2): This class can only be used with the compiler argument '-Xopt-in=kotlin.RequiresOptIn'
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/common/instance/tail/LogTailer.kt: (9, 2): This class can only be used with the compiler argument '-Xopt-in=kotlin.RequiresOptIn'
w: /Users/krystian.panek/Projects/github-pun-ky/gradle-aem-plugin/src/main/kotlin/com/cognifide/gradle/aem/common/mvn/MvnGav.kt: (15, 23): 'XmlParser' is deprecated. Deprecated in Java