K2: Add new tests for PCLA implementation

Many of them have been found & minimized at FP tests/user projects

^KT-59791 Fixed

compiler/testData/diagnostics/tests/inference/builderInference/assignmentUsingIncompletePCLACall.kt

@@ -0,0 +1,20 @@
+// FIR_IDENTICAL
+
+class Controller<T> {
+    fun yield(t: T): Boolean = true
+}
+
+fun <S> generate(g: suspend Controller<S>.() -> Unit): S = TODO()
+fun <T, R> T.bar(x: (T) -> R): R = TODO()
+
+var children: String = TODO()
+
+fun main(key: String?, v: Number) {
+    generate {
+        yield("")
+        // Here, elvis-synthetic call is not completed yet, but it's variable K is already fixed
+        // Assignment is used, because for that (outside of PCLA) we would use FULL completion
+        children = key ?: v.bar { it.toString() }
+    }.length
+}
+