[Platform API] Introduce fundamental abstraction of Platform

This is a large commit, which introduces general API for working with
abstraction of Platform.

- Add new abstraction to 'core' - SimplePlatform - which represents
exactly one platform
  - Clients are strongly prohibited to create instances of SimplePlatform
  by hand, instead, corresponding *Platforms abstraction should be used
  (e.g. JvmPlatforms, JsPlatforms, KonanPlatforms)

- Move TargetPlatform to 'core', it represents now a collection of
SimplePlatforms
  - Clients are strongly encouraged to use TargetPlatform
    (not SimplePlatform) in API, to enforce checks for multiplatform

- Provide a helper-extensions to work with TargetPlatform
(in particular, for getting a specific component platform)

- Remove MultiTargetPlatform in favour of TargetPlatform
  - Notably, this commit leaves another widely used duplicated abstraction,
    namely, IdePlatform. For the sake sanity, removal of IdePlatform is
    extracted in the separate commit.

compiler/tests-common/tests/org/jetbrains/kotlin/resolve/lazy/lazyResolveTestUtils.kt

@@ -22,17 +22,17 @@ import org.jetbrains.kotlin.analyzer.LanguageSettingsProvider
 import org.jetbrains.kotlin.analyzer.ModuleContent
 import org.jetbrains.kotlin.analyzer.ModuleInfo
 import org.jetbrains.kotlin.analyzer.ResolverForProjectImpl
-import org.jetbrains.kotlin.analyzer.common.CommonPlatform
-import org.jetbrains.kotlin.analyzer.common.CommonPlatformCompilerServices
 import org.jetbrains.kotlin.container.get
 import org.jetbrains.kotlin.context.ProjectContext
 import org.jetbrains.kotlin.load.kotlin.PackagePartProvider
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.resolve.PlatformDependentCompilerServices
-import org.jetbrains.kotlin.resolve.TargetPlatform
+import org.jetbrains.kotlin.platform.TargetPlatform
+import org.jetbrains.kotlin.platform.jvm.JvmPlatforms
 import org.jetbrains.kotlin.resolve.jvm.JvmResolverForModuleFactory
 import org.jetbrains.kotlin.resolve.jvm.JvmPlatformParameters
+import org.jetbrains.kotlin.resolve.jvm.platform.JvmPlatformCompilerServices
 
 fun createResolveSessionForFiles(
         project: Project,
@@ -67,8 +67,8 @@ private class TestModule(val dependsOnBuiltIns: Boolean) : ModuleInfo {
                 ModuleInfo.DependencyOnBuiltIns.NONE
 
     override val platform: TargetPlatform
-        get() = CommonPlatform
+        get() = JvmPlatforms.defaultJvmPlatform
 
     override val compilerServices: PlatformDependentCompilerServices?
-        get() = CommonPlatformCompilerServices
+        get() = JvmPlatformCompilerServices
 }