[FIR2IR] Consolidate type approximation

This commit gets rid of the redundant typeApproximatorConfiguration
in Fir2IrTypeConverter and uses the type approximator for captured
types instead of the manual approximation used before.

This fixes the nullability of approximated captured types, which fixes
a runtime error in WASM.

This also brings K2 IR closer to K1 IR in one test.

#KT-64261 Fixed

compiler/testData/ir/irText/types/genericFunWithStar.fir.ir.txt

@@ -77,7 +77,7 @@ FILE fqName:<root> fileName:/genericFunWithStar.kt
       BLOCK_BODY
         RETURN type=kotlin.Nothing from='public final fun bar (vararg serializers: <root>.I<*>): <root>.I<*> declared in <root>.Box'
           CALL 'public abstract fun foo <F> (tSerializer: <root>.I<F of <root>.Box.foo>): <root>.I<<root>.Box<F of <root>.Box.foo>> declared in <root>.Box' type=<root>.I<out <root>.Box<*>> origin=null
-            <F>: <root>.IFoo
+            <F>: <root>.IBase
             $this: GET_VAR '<this>: <root>.Box<T of <root>.Box> declared in <root>.Box.bar' type=<root>.Box<T of <root>.Box> origin=null
             tSerializer: CALL 'public final fun get (index: kotlin.Int): T of kotlin.Array declared in kotlin.Array' type=<root>.I<*> origin=null
               $this: GET_VAR 'serializers: kotlin.Array<out <root>.I<*>> declared in <root>.Box.bar' type=kotlin.Array<out <root>.I<*>> origin=null

compiler/testData/ir/irText/types/genericFunWithStar.fir.kt.txt

@@ -20,7 +20,7 @@ abstract class Box<T> : IFoo, IBar where T : IFoo, T : IBar {
   abstract fun <F> foo(tSerializer: I<F>): I<Box<F>> where F : IFoo, F : IBar
 
   fun bar(vararg serializers: I<*>): I<*> {
-    return <this>.foo<IFoo>(tSerializer = serializers.get(index = 0))
+    return <this>.foo<IBase>(tSerializer = serializers.get(index = 0))
   }
 
 }