Leverage existing psi2ir function declaration generator in plugin

This seems to be the only reasonable way to provide function declarations with
_correctly_ substituted type parameters without rewriting logic from scratch;
correctly scoped type parameters in IR are now required in serialization
plugin by all backends.

Also fix some missing upper bounds.

compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/klib.kt

@@ -47,6 +47,7 @@ import org.jetbrains.kotlin.psi.KtFile
 import org.jetbrains.kotlin.psi2ir.Psi2IrConfiguration
 import org.jetbrains.kotlin.psi2ir.Psi2IrTranslator
 import org.jetbrains.kotlin.psi2ir.generators.GeneratorContext
+import org.jetbrains.kotlin.psi2ir.generators.createGeneratorContext
 import org.jetbrains.kotlin.psi2ir.generators.GeneratorExtensions
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.BindingContextUtils
@@ -241,7 +242,7 @@ private fun runAnalysisAndPreparePsi2Ir(depsDescriptors: ModulesStructure): Gene
     val mangler = JsManglerDesc
     val signaturer = IdSignatureDescriptor(mangler)
 
-    return GeneratorContext(
+    return createGeneratorContext(
         Psi2IrConfiguration(),
         analysisResult.moduleDescriptor,
         analysisResult.bindingContext,