De-duplicate sonar job in the CI (#1238)

* De-duplicate sonar job in the CI

* Remove workaround for `src/*/kotlin` folders

* Downgrade the sonarqube plugin version

* Try increasing workers for this job, since it's quite slow

* Warn about regression in latest sonarqube release

* Forbid backups to prevent cryptographic issues

build.gradle.kts

@@ -143,22 +143,6 @@ sonar {
     }
 }
 
-allprojects {
-    val projectDir = projectDir.toString()
-    sonar {
-        properties {
-            // Note: folders `kotlin` are not supported (yet), I asked on their side: https://community.sonarsource.com/t/82824
-            // As a workaround provide the path in `sonar.sources` property.
-            if (File("$projectDir/src/main/kotlin").exists()) {
-                property("sonar.sources", "src/main/kotlin")
-            }
-            if (File("$projectDir/src/test/kotlin").exists()) {
-                property("sonar.tests", "src/test/kotlin")
-            }
-        }
-    }
-}
-
 allprojects {
     tasks.withType<Test> {
         maxParallelForks = (Runtime.getRuntime().availableProcessors() / 2).coerceAtLeast(1)