[Gradle] Implement 'Project.kotlinPropertiesProvider' extension

This extension should increase discoverability over the previous
'PropertiesProvider(project)' API

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinProperties.kt

@@ -145,7 +145,9 @@ internal class PropertiesProvider private constructor(private val project: Proje
 
     var mpp13XFlagsSetByPlugin: Boolean
         get() = booleanProperty("kotlin.internal.mpp.13X.flags.setByPlugin") ?: false
-        set(value) { project.extensions.extraProperties.set("kotlin.internal.mpp.13X.flags.setByPlugin", "$value") }
+        set(value) {
+            project.extensions.extraProperties.set("kotlin.internal.mpp.13X.flags.setByPlugin", "$value")
+        }
 
     val mppHierarchicalStructureByDefault: Boolean
         get() = booleanProperty(KOTLIN_MPP_HIERARCHICAL_STRUCTURE_BY_DEFAULT) ?: false
@@ -429,5 +431,7 @@ internal class PropertiesProvider private constructor(private val project: Proje
                 return get(CACHED_PROVIDER_EXT_NAME) as? PropertiesProvider
                     ?: PropertiesProvider(project) // Fallback if multiple class loaders are involved
             }
+
+        internal val Project.kotlinPropertiesProvider get() = PropertiesProvider(this)
     }
 }