IR: add type parameter to IrMemberAccessExpression and some subclasses

This is needed to get rid of the diamond hierarchy:

                 IrMemberAccessExpression
                 /                       \
                /                         \
IrFunctionAccessExpression     IrCallableReference
                \                      /
                 \                    /
                   IrFunctionReference

In the subsequent commit, IrFunctionReference no longer inherits from
IrFunctionAccessExpression; the more precise type of `val symbol:
IrFunctionSymbol` is now carried via the generic type argument.

This will help to refactor IR element hierarchy from interfaces to
classes, improving performance of visitors and transformers.

plugins/kotlin-serialization/kotlin-serialization-compiler/src/org/jetbrains/kotlinx/serialization/compiler/backend/ir/GeneratorHelpers.kt

@@ -71,7 +71,7 @@ interface IrBuilderExtension {
         callee: IrFunctionSymbol,
         vararg args: IrExpression,
         typeHint: IrType? = null
-    ): IrMemberAccessExpression {
+    ): IrMemberAccessExpression<*> {
         assert(callee.isBound) { "Symbol $callee expected to be bound" }
         val returnType = typeHint ?: callee.run { owner.returnType }
         val call = irCall(callee, type = returnType)
@@ -86,7 +86,7 @@ interface IrBuilderExtension {
         typeArguments: List<IrType?>,
         valueArguments: List<IrExpression>,
         returnTypeHint: IrType? = null
-    ): IrMemberAccessExpression =
+    ): IrMemberAccessExpression<*> =
         irInvoke(
             dispatchReceiver,
             callee,