Add constraints between two different stub variables instead of creating constraint error due to T1 isn't subtype of T2

^KT-44241 Fixed

compiler/testData/codegen/box/inference/builderInference/constraintsBetweenTwoStubVariables.kt

@@ -0,0 +1,25 @@
+// !LANGUAGE: +UnrestrictedBuilderInference
+// WITH_RUNTIME
+
+import kotlin.experimental.ExperimentalTypeInference
+
+class Foo<K11, K22>(val key: K11) {
+    fun emit1(key: K11) {}
+    fun get(): K11 = null as K11
+    fun emit2(key: K22) {}
+}
+
+@OptIn(ExperimentalTypeInference::class)
+fun <K1, K2> build(@kotlin.BuilderInference builder: Foo<K1, K2>.() -> Unit) {}
+
+fun run(x: Int) {
+    build {
+        emit1(x)
+        emit2(get()) // We shouldn't report type mismatch, instead we should add constraint StubTypeVariable(K2) >: StubTypeVariable(K1), then infer K2 into Int among K1
+    }
+}
+
+fun box(): String {
+    run(1)
+    return "OK"
+}

compiler/testData/codegen/box/inference/builderInference/intersect.kt

@@ -1,7 +1,6 @@
 // !LANGUAGE: +UnrestrictedBuilderInference
 // WITH_RUNTIME
 // TARGET_BACKEND: JVM
-// IGNORE_BACKEND_FIR: JVM_IR
 // DONT_TARGET_EXACT_BACKEND: WASM
 
 // FILE: Test.java
@@ -37,15 +36,6 @@ fun box(): String {
         intersect(getIn(), Test.foo(getIn()))
         intersect(Test.foo(getIn()), Test.foo(getIn()))
         intersect(Test.foo(getIn()), getIn())
-
-        build2 {
-            emit(1)
-            intersect(this@build.getIn(), getIn())
-            intersect(getIn(), Test.foo(this@build.getIn()))
-            intersect(Test.foo(this@build.getIn()), Test.foo(getIn()))
-            intersect(Test.foo(getIn()), this@build.getIn())
-            ""
-        }
         ""
     }
     return "OK"

compiler/testData/codegen/box/inference/builderInference/kt44241.kt

@@ -0,0 +1,23 @@
+// !LANGUAGE: +UnrestrictedBuilderInference
+// WITH_RUNTIME
+
+import kotlin.experimental.ExperimentalTypeInference
+class A
+class B<K> {}
+class Scope<K11, K22>(
+    val key: K11,
+) {
+    fun emit(key: K22) {}
+}
+
+@OptIn(ExperimentalTypeInference::class)
+fun <K1, K2> B<K1>.scoped(@kotlin.BuilderInference binder: Scope<K1, K2>.() -> Unit) {}
+
+fun run(x: B<A>) {
+    x.scoped { emit(key) }
+}
+
+fun box(): String {
+    run(B<A>())
+    return "OK"
+}