[AA] FE10 compiler facility: Remove old backend support

- Old backend support is not needed in `KtFe10CompilerFacility` anymore,
  because it has been removed for the bytecode tool window, which was
  the only user. The old backend is slated to be removed entirely.

^KTIJ-24522

analysis/analysis-api-fe10/src/org/jetbrains/kotlin/analysis/api/descriptors/components/KtFe10CompilerFacility.kt

diff --git a/analysis/analysis-api-fe10/src/org/jetbrains/kotlin/analysis/api/descriptors/components/KtFe10CompilerFacility.kt b/analysis/analysis-api-fe10/src/org/jetbrains/kotlin/analysis/api/descriptors/components/KtFe10CompilerFacility.kt
index 406def4..fa4ede3 100644
--- a/analysis/analysis-api-fe10/src/org/jetbrains/kotlin/analysis/api/descriptors/components/KtFe10CompilerFacility.kt
+++ b/analysis/analysis-api-fe10/src/org/jetbrains/kotlin/analysis/api/descriptors/components/KtFe10CompilerFacility.kt
@@ -5,8 +5,8 @@
 
 package org.jetbrains.kotlin.analysis.api.descriptors.components
 
-import org.jetbrains.kotlin.analysis.api.components.KtCompilerFacility
 import org.jetbrains.kotlin.analysis.api.components.KtCompilationResult
+import org.jetbrains.kotlin.analysis.api.components.KtCompilerFacility
 import org.jetbrains.kotlin.analysis.api.components.KtCompilerTarget
 import org.jetbrains.kotlin.analysis.api.descriptors.Fe10AnalysisFacade.AnalysisMode
 import org.jetbrains.kotlin.analysis.api.descriptors.KtFe10AnalysisSession
@@ -20,7 +20,6 @@
 import org.jetbrains.kotlin.backend.jvm.JvmGeneratorExtensionsImpl
 import org.jetbrains.kotlin.backend.jvm.JvmIrCodegenFactory
 import org.jetbrains.kotlin.backend.jvm.jvmPhases
-import org.jetbrains.kotlin.codegen.DefaultCodegenFactory
 import org.jetbrains.kotlin.codegen.KotlinCodegenFacade
 import org.jetbrains.kotlin.codegen.state.GenerationState
 import org.jetbrains.kotlin.config.*
@@ -36,8 +35,6 @@
  * Whether unbound IR symbols should be stubbed instead of linked.
  * This should be enabled if the compiled file could refer to symbols defined in another file of the same module.
  * Such symbols are not compiled (only the file is passed to the backend) and so they cannot be linked from a dependency.
- *
- * The option only has an effect when the IR backend is active.
  */
 val STUB_UNBOUND_IR_SYMBOLS: CompilerConfigurationKey<Boolean> = CompilerConfigurationKey<Boolean>("stub unbound IR symbols")
 
@@ -64,7 +61,6 @@
                 put(JVMConfigurationKeys.DO_NOT_CLEAR_BINDING_CONTEXT, true)
             }
 
-        val useIrBackend = effectiveConfiguration.getBoolean(JVMConfigurationKeys.IR)
         val disableInline = effectiveConfiguration.getBoolean(CommonConfigurationKeys.DISABLE_INLINE)
 
         // The binding context needs to be built from all files with reachable inline functions, as such files may contain classes whose
@@ -84,11 +80,7 @@
 
         // The IR backend will try to regenerate object literals defined in inline functions from generated class files during inlining.
         // Hence, we need to be aware of which object declarations are defined in the relevant inline functions.
-        val inlineObjectDeclarations = when {
-            useIrBackend -> inlineAnalyzer.inlineObjectDeclarations()
-            else -> setOf()
-        }
-
+        val inlineObjectDeclarations = inlineAnalyzer.inlineObjectDeclarations()
         val inlineObjectDeclarationFiles = inlineObjectDeclarations.mapTo(mutableSetOf()) { it.containingKtFile }
 
         class GenerateClassFilter : GenerationState.GenerateClassFilter() {
@@ -114,10 +106,7 @@
 
         val generateClassFilter = GenerateClassFilter()
 
-        val codegenFactory = when {
-            useIrBackend -> createJvmIrCodegenFactory(effectiveConfiguration)
-            else -> DefaultCodegenFactory
-        }
+        val codegenFactory = createJvmIrCodegenFactory(effectiveConfiguration)
 
         val state = GenerationState.Builder(
             file.project,
@@ -159,7 +148,7 @@
     }
 
     private fun createJvmIrCodegenFactory(configuration: CompilerConfiguration): JvmIrCodegenFactory {
-        val stubUnboundIrSymbols = configuration[STUB_UNBOUND_IR_SYMBOLS] ?: false
+        val stubUnboundIrSymbols = configuration[STUB_UNBOUND_IR_SYMBOLS] == true
 
         val jvmGeneratorExtensions = if (stubUnboundIrSymbols) {
             object : JvmGeneratorExtensionsImpl(configuration) {