Control flow graph for safe calls corrected #KT-10913 Fixed

Also #KT-10186 Fixed
Also #KT-5198 Fixed

compiler/testData/diagnostics/tests/controlFlowAnalysis/throwInLambda.kt

@@ -0,0 +1,12 @@
+// See KT-10913 Bogus unreachable code warning
+
+fun fn() : String? = null
+fun foo(): String {
+    val x = fn()?.let { throw Exception() } ?: "unreachable?"
+    return x
+}
+fun bar(): String {
+    val x = fn() ?: return ""
+    <!UNREACHABLE_CODE!>val <!UNUSED_VARIABLE!>y<!> =<!> x<!UNNECESSARY_SAFE_CALL!>?.<!>let { throw Exception() } <!USELESS_ELVIS, UNREACHABLE_CODE!>?: "unreachable"<!>
+    <!UNREACHABLE_CODE!>return y<!>
+}