[Test] Add ability to specify main class in Box tests

Also slightly refactor some existing services to make them more idiomatic

compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/services/RuntimeClasspathProvider.kt

@@ -5,14 +5,15 @@
 
 package org.jetbrains.kotlin.test.services
 
+import org.jetbrains.kotlin.test.model.TestModule
 import java.io.File
 
-abstract class RuntimeClasspathProvider {
-    abstract fun runtimeClassPaths(): List<File>
+abstract class RuntimeClasspathProvider(val testServices: TestServices) {
+    abstract fun runtimeClassPaths(module: TestModule): List<File>
 }
 
-class RuntimeClasspathProviderHolder(val providers: List<RuntimeClasspathProvider>) : TestService
+class RuntimeClasspathProvidersContainer(val providers: List<RuntimeClasspathProvider>) : TestService
 
-private val TestServices.runtimeClasspathProviderHolder: RuntimeClasspathProviderHolder by TestServices.testServiceAccessor()
+private val TestServices.runtimeClasspathProviderContainer: RuntimeClasspathProvidersContainer by TestServices.testServiceAccessor()
 val TestServices.runtimeClasspathProviders: List<RuntimeClasspathProvider>
-    get() = runtimeClasspathProviderHolder.providers
+    get() = runtimeClasspathProviderContainer.providers

compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/services/TestServices.kt

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.test.services
 
 import org.jetbrains.kotlin.fir.utils.ArrayMapAccessor
 import org.jetbrains.kotlin.fir.utils.ComponentArrayOwner
+import org.jetbrains.kotlin.fir.utils.NullableArrayMapAccessor
 import org.jetbrains.kotlin.fir.utils.TypeRegistry
 import kotlin.reflect.KClass
 
@@ -31,6 +32,10 @@ class TestServices : ComponentArrayOwner<TestService, TestService>(){
         inline fun <reified T : TestService> testServiceAccessor(): ArrayMapAccessor<TestService, TestService, T> {
             return generateAccessor(T::class)
         }
+
+        inline fun <reified T : TestService> nullableTestServiceAccessor(): NullableArrayMapAccessor<TestService, TestService, T> {
+            return generateNullableAccessor(T::class)
+        }
     }
 
     fun register(data: ServiceRegistrationData) {