Report warning on unused entities that can be renamed to _

Currently it's all about lambda parameters/destructuring entries

 #KT-14347 In Progress

compiler/testData/diagnostics/tests/declarationChecks/kt2643MultiDeclInControlFlow.kt

@@ -7,7 +7,7 @@ class C {
 }
 
 fun test1(c: C) {
-    val (a, <!UNUSED_VARIABLE!>b<!>) = c
+    val (<!UNUSED_VARIABLE!>a<!>, <!UNUSED_VARIABLE!>b<!>) = c
 }
 
 fun test2(c: C) {
@@ -16,7 +16,7 @@ fun test2(c: C) {
 }
 
 fun test3(c: C) {
-    var (a, <!UNUSED_VARIABLE!>b<!>) = c
+    var (<!ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE!>a<!>, <!UNUSED_VARIABLE!>b<!>) = c
     <!UNUSED_VALUE!>a =<!> 3
 }
 
@@ -24,4 +24,4 @@ fun test4(c: C) {
     var (<!VARIABLE_WITH_REDUNDANT_INITIALIZER!>a<!>, <!UNUSED_VARIABLE!>b<!>) = c
     a = 3
     a + 1
-}
+}