[IR] Minor: Make some checker code public

Required for the next commit.

KT-76601

Author: mcpiroman

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/ScopeStack.kt

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.backend.common
 
-internal class ScopeStack<E> {
+class ScopeStack<E> {
     private class Scope<E>(val isGlobal: Boolean) {
         val values = mutableSetOf<E>()
     }

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/checkers/IrElementChecker.kt

@@ -13,7 +13,7 @@ import kotlin.reflect.KClass
 abstract class IrElementChecker<in E : IrElement>(
     elementClass: KClass<in E>,
 ) {
-    internal abstract fun check(element: E, context: CheckerContext)
+    abstract fun check(element: E, context: CheckerContext)
 }
 
 internal fun <E : IrElement> List<IrElementChecker<E>>.check(element: E, context: CheckerContext) {

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/checkers/context/CheckerContext.kt

@@ -18,7 +18,7 @@ import org.jetbrains.kotlin.ir.declarations.IrTypeParametersContainer
 import org.jetbrains.kotlin.ir.symbols.IrTypeParameterSymbol
 import org.jetbrains.kotlin.ir.symbols.IrValueSymbol
 
-internal class CheckerContext(
+class CheckerContext(
     val irBuiltIns: IrBuiltIns,
     val checkInlineFunctionUseSites: InlineFunctionUseSiteChecker?,
     val file: IrFile,

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/checkers/context/ContextUpdater.kt

@@ -10,7 +10,7 @@ import org.jetbrains.kotlin.ir.IrElement
 /**
  * Manages temporary updates to a [CheckerContext] during the processing of an [IrElement].
  */
-internal interface ContextUpdater {
+interface ContextUpdater {
     /**
      * Temporarily updates the [context]  based on the given [element], executes [block] within the updated context,
      * and then restores the context to its original state.