[Injection] Introduce PlatformSpecificExtensions and PlatformExtensionsClashResolver

This commit introduces the ability to register a PlatformExtensionClashResolver
in a container. Each PlatformExtensionClashResolver has a corresponding
PlatformSpecificExtensions.

If, during container composition, several instances of
PlatformSpecificExtensions were registred, instead of throwing
InvalidCardinalityException, corresponding PlatformExtensionClashResolver
will be asked to resolve clash.

This allows to make injection more composable and less coupled across
different contributors of service, providing a basis for such motivating
cases as composing containers with both JS and JVM services (for analysis
of multiplatform modules).
Previously, that would be impossible:
a) JS would inject default instances for some services which would clash
with non-default JVM services (like SyntheticScopes)
b) Also, there are a very few services for which *both* platforms provide
non-default implementations, so they should be merged manually on
case-by-case basis (e.g., IdentifierChecker)

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignature.kt

@@ -17,6 +17,8 @@
 package org.jetbrains.kotlin.resolve.calls.results
 
 import org.jetbrains.kotlin.container.DefaultImplementation
+import org.jetbrains.kotlin.container.PlatformExtensionsClashResolver
+import org.jetbrains.kotlin.container.PlatformSpecificExtension
 import org.jetbrains.kotlin.descriptors.CallableDescriptor
 import org.jetbrains.kotlin.descriptors.MemberDescriptor
 import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
@@ -30,7 +32,7 @@ interface SpecificityComparisonCallbacks {
 }
 
 @DefaultImplementation(impl = TypeSpecificityComparator.NONE::class)
-interface TypeSpecificityComparator {
+interface TypeSpecificityComparator : PlatformSpecificExtension<TypeSpecificityComparator> {
     fun isDefinitelyLessSpecific(specific: KotlinTypeMarker, general: KotlinTypeMarker): Boolean
 
     object NONE : TypeSpecificityComparator {