[IR] Add isAssignable property to IrValueParameter.

Use it to check that only the value parameters that are explicitly
marked assignable are assigned.

Currently, the only parameters marked assignable are those for
default argument stubs.

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt

@@ -356,7 +356,7 @@ internal fun IrDeclarationParent.declareThisReceiverParameter(
         symbolTable.irFactory.createValueParameter(
             startOffset, endOffset, thisOrigin, symbol,
             Name.special("<this>"), -1, thisType,
-            varargElementType = null, isCrossinline = false, isNoinline = false
+            varargElementType = null, isCrossinline = false, isNoinline = false, isAssignable = false
         ).apply {
             this.parent = this@declareThisReceiverParameter
             receiverDescriptor.bind(this)

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt

@@ -256,7 +256,7 @@ class Fir2IrDeclarationStorage(
                     startOffset, endOffset, IrDeclarationOrigin.DEFINED, symbol,
                     Name.special("<set-?>"), 0, type,
                     varargElementType = null,
-                    isCrossinline = false, isNoinline = false
+                    isCrossinline = false, isNoinline = false, isAssignable = false
                 ).apply {
                     this.parent = parent
                     descriptor.bind(this)
@@ -843,7 +843,7 @@ class Fir2IrDeclarationStorage(
                     valueParameter.name, index, type,
                     if (!valueParameter.isVararg) null
                     else valueParameter.returnTypeRef.coneType.arrayElementType()?.toIrType(typeContext),
-                    valueParameter.isCrossinline, valueParameter.isNoinline
+                    valueParameter.isCrossinline, valueParameter.isNoinline, false
                 ).apply {
                     descriptor.bind(this)
                     if (valueParameter.defaultValue.let {

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/AdapterGenerator.kt

@@ -274,7 +274,8 @@ internal class AdapterGenerator(
                 type,
                 varargElementType = null,
                 isCrossinline = false,
-                isNoinline = false
+                isNoinline = false,
+                isAssignable = false
             ).also { irAdapterValueParameter ->
                 descriptor.bind(irAdapterValueParameter)
                 irAdapterValueParameter.parent = adapterFunction

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/DataClassMembersGenerator.kt

@@ -281,7 +281,7 @@ class DataClassMembersGenerator(val components: Fir2IrComponents) {
             ) { symbol ->
                 components.irFactory.createValueParameter(
                     UNDEFINED_OFFSET, UNDEFINED_OFFSET, origin, symbol, name, index, type, null,
-                    isCrossinline = false, isNoinline = false
+                    isCrossinline = false, isNoinline = false, isAssignable = false
                 )
             }.apply {
                 parent = irFunction