[Build] Migrate most of the build logic from Project.buildDir usage

It's going to be deprecated in Gradle 8.3

There's currently no way to pass a `org.gradle.api.provider.Provider` to the JavaExec.systemProperty or Test.systemProperty. There's a workaround using `org.gradle.process.CommandLineArgumentProvider`, but I intentionally don't rework these calls as Gradle is going to allow passing providers to configure system properties: https://github.com/gradle/gradle/issues/12247#issuecomment-1568427242
^KTI-1473 In Progress

gradle/checkArtifacts.gradle.kts

@@ -5,10 +5,10 @@ import java.util.zip.ZipFile
 val isTeamcityBuild = project.hasProperty("teamcity") || System.getenv("TEAMCITY_VERSION") != null
 
 val distDir: String by rootProject.extra
-val repoDir: String = "${rootProject.buildDir}/repo"
 val kotlinVersion: String by rootProject.extra
 
 val checkMavenArtifacts = tasks.register("checkMavenArtifacts") {
+    val repoDir = rootProject.layout.buildDirectory.dir("repo")
     doLast {
         fileTree(repoDir).checkArtifacts { zip ->
             if (!zip.name.endsWith("-sources.jar"))