[Analysis API] add tests for delegate field

^KT-64584

analysis/low-level-api-fir/testData/getOrBuildFirBinary/delegate.kt

@@ -0,0 +1,11 @@
+// DECLARATION_TYPE: org.jetbrains.kotlin.psi.KtClass
+class I(private val p: A) : A by p
+
+interface A {
+    var Int.zoo: Unit
+    fun foo()
+    fun Int.smth(): Short
+    val foo: Int
+    var bar: Long
+    val Int.doo: String
+}

analysis/low-level-api-fir/testData/getOrBuildFirBinary/delegate.txt

@@ -0,0 +1,16 @@
+KT element: KtClass
+KT element text:
+public final class I public constructor(p: A) : A {
+    private final val p: A /* compiled code */
+}
+FIR element: FirRegularClassImpl
+FIR source kind: KtRealSourceElementKind
+
+FIR element rendered:
+public final [ResolvedTo(BODY_RESOLVE)] class I : R|A| {
+    private final [ResolvedTo(BODY_RESOLVE)] val p: R|A|
+
+
+    public [ResolvedTo(BODY_RESOLVE)] [ContainingClassKey=I] constructor([ResolvedTo(BODY_RESOLVE)] p: R|A|): R|I|
+
+}