Introduce tooling model for Kotlin gradle projects

A KotlinProject model for Gradle projects including Kotlin (JVM, JS or
common) plugins is introduced. Its model builder KotlinModelBuilder
produces an implementation of these models and can be queried through
the Gradle Tooling API when needed. Model builder is registered in the
corresponding Kotlin Gradle plugins.

Model definition should be published as a separate artifact in public
repositories so it can be consumed when needed.

settings.gradle

@@ -141,6 +141,7 @@ include ":kotlin-build-common",
         ":tools:kotlinp",
         ":kotlin-gradle-plugin-api",
         ":kotlin-gradle-plugin",
+        ":kotlin-gradle-plugin-model",
         ":kotlin-gradle-plugin-test-utils-embeddable",
         ":kotlin-gradle-plugin-integration-tests",
         ":kotlin-allopen",
@@ -251,6 +252,7 @@ project(':tools:kotlin-stdlib-gen').projectDir = "$rootDir/libraries/tools/kotli
 project(':tools:kotlinp').projectDir = "$rootDir/libraries/tools/kotlinp" as File
 project(':kotlin-gradle-plugin-api').projectDir = "$rootDir/libraries/tools/kotlin-gradle-plugin-api" as File
 project(':kotlin-gradle-plugin').projectDir = "$rootDir/libraries/tools/kotlin-gradle-plugin" as File
+project(':kotlin-gradle-plugin-model').projectDir = "$rootDir/libraries/tools/kotlin-gradle-plugin-model" as File
 project(':kotlin-gradle-plugin-test-utils-embeddable').projectDir = "$rootDir/libraries/tools/kotlin-gradle-plugin-test-utils-embeddable" as File
 project(':kotlin-gradle-plugin-integration-tests').projectDir = "$rootDir/libraries/tools/kotlin-gradle-plugin-integration-tests" as File
 project(':kotlin-allopen').projectDir = "$rootDir/libraries/tools/kotlin-allopen" as File