Fix Android ap option providers as Kapt task nested inputs

1) Exclude the providers arguments from the kapt inputs, as the values
may contain absolute paths, may be output properties etc. The providers
should correctly annotate their inputs.

2) Fix the options passed to kapt as 'value=option' (leading to all the
options collapse into one with the null key), use 'key=option' instead
to make Kapt pass them as '-Aoption'.

Issue #KT-23866 Fixed
Issue #KT-25027 Fixed

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

@@ -45,6 +45,9 @@ enum class FilesOptionKind {
     // such as output directories, inputs or classpath options.
 }
 
+/** Defines a subplugin option that should be excluded from Gradle input/output checks */
+open class InternalSubpluginOption(key: String, value: String) : SubpluginOption(key, value)
+
 interface KotlinGradleSubplugin<in KotlinCompile : AbstractCompile> {
     fun isApplicable(project: Project, task: AbstractCompile): Boolean