CocoaPods: Basic support

This patch adds a separate Gradle plugin allowing
a user to import Kotlin/Native modules in Cocoapods
projects and use Cocoapods dependencies in Kotlin
code via cinterop.

The plugin when applied does the following things:

1. Add a framework binary for each supported (iOS
   or macOS) platform in the project.

2. Add a Cocoapods extension allowing one to configure
   Cocoapods dependencies of the project.

3. Create cinterop tasks for each dependency from the
   previous point. The tasks are added for main
   compilations of each supported platform.

4. Add a task to generate a podspec-file which includes
   the framework from the point 1, script to
   build it and dependencies from the point 2.

So the Cocoapods import procedure is the following:

1. A user runs `./gradlew generatePodspec`. The plugin
   creates a podspec-file with all dependencies.

2. The user adds a dependency on this podspec in his Podfile
   and runs `pod install`. Cocoapods downloads dependencies
   and configures user's XCode project.

3. The user runs XCode build. XCode builds dependencies and then
   runs Gradle build. Gradle performs interop processing and
   builds the Kotlin framework. Compiler options and header
   search paths are passed in the Gradle from XCode environment
   variables. After that the final application is built by XCode.

Issue #KT-30269 Fixed

libraries/tools/kotlin-gradle-plugin/build.gradle.kts

@@ -90,7 +90,9 @@ tasks {
         for ((name, value) in propertiesToExpand) {
             inputs.property(name, value)
         }
-        expand("projectVersion" to project.version)
+        filesMatching("project.properties") {
+            expand("projectVersion" to project.version)
+        }
     }
 
     named<Jar>("jar") {