IR: use DescriptorBySignatureFinder in DeclarationStubGenerator

Duplicating code that was used for the same purpose in
DeclarationStubGenerator is removed.

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/analysis/FirAnalyzerFacade.kt

@@ -103,7 +103,8 @@ class FirAnalyzerFacade(
 
     override fun convertToIr(extensions: GeneratorExtensions): Fir2IrResult {
         if (_scopeSession == null) runResolution()
-        val signaturer = JvmIdSignatureDescriptor(JvmDescriptorMangler(null))
+        val mangler = JvmDescriptorMangler(null)
+        val signaturer = JvmIdSignatureDescriptor(mangler)
 
         val commonFirFiles = session.moduleData.dependsOnDependencies
             .map { it.session }
@@ -112,7 +113,7 @@ class FirAnalyzerFacade(
 
         return Fir2IrConverter.createModuleFragment(
             session, _scopeSession!!, firFiles!! + commonFirFiles,
-            languageVersionSettings, signaturer,
+            languageVersionSettings, mangler, signaturer,
             extensions, FirJvmKotlinMangler(session), IrFactoryImpl,
             FirJvmVisibilityConverter,
             Fir2IrJvmSpecialAnnotationSymbolProvider(),

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/pipeline/convertToIr.kt

@@ -29,7 +29,8 @@ fun FirSession.convertToIr(
     extensions: GeneratorExtensions,
     irGeneratorExtensions: Collection<IrGenerationExtension>
 ): Fir2IrResult {
-    val signaturer = JvmIdSignatureDescriptor(JvmDescriptorMangler(null))
+    val mangler = JvmDescriptorMangler(null)
+    val signaturer = JvmIdSignatureDescriptor(mangler)
 
     val commonFirFiles = moduleData.dependsOnDependencies
         .map { it.session }
@@ -38,7 +39,7 @@ fun FirSession.convertToIr(
 
     return Fir2IrConverter.createModuleFragment(
         this, scopeSession, firFiles + commonFirFiles,
-        languageVersionSettings, signaturer,
+        languageVersionSettings, mangler, signaturer,
         extensions, FirJvmKotlinMangler(this), IrFactoryImpl,
         FirJvmVisibilityConverter,
         Fir2IrJvmSpecialAnnotationSymbolProvider(),