[Gradle] Add 'validatePlugins' tasks for Gradle plugin dependencies

Gradle 8 has removed "validate-external-gradle-plugin" plugin which we
used before to run validate task inputs proper annotations.

With this change, every Gradle dependency that is not published as a
Gradle plugin but uses Gradle API types is also running
'validatedPlugins' task registered manually via a build script.

^KT-59827 Fixed

build.gradle.kts

@@ -400,6 +400,7 @@ val gradlePluginProjects = listOf(
     ":kotlin-gradle-plugin-idea",
     ":kotlin-gradle-plugin-idea-proto",
     ":kotlin-gradle-plugin-kpm-android",
+    ":kotlin-gradle-plugin-model",
     ":kotlin-gradle-plugin-tcs-android",
     ":kotlin-allopen",
     ":kotlin-noarg",