FIR IDE: quickfix for WrapWithSafeLetCall

There is some behavior change regarding the new WrapWithSafeLetCall quickfix

1. it now works correctly on binary expressions by wrapping it with `()`
2. it now looks for a nullable position upward and do the modification there,
   if possible. For example, consider the following code

   ```
   fun bar(s: String): String = s

   fun test(s: String?) {
     bar(bar(bar(<caret>s)))
   }
   ```

   After applying this fix, FE1.0 yields

   ```
   bar(bar(s?.let { bar(it) }))
   ```

   while the new implementation yields

   ```
   s?.let { bar(bar(bar(it))) }
   ```

   This behavior aligns with FE1.0 if `bar` accepts nullable values.

idea/testData/quickfix/wrapWithSafeLetCall/nullableBinaryExpression.fir.kt.after

@@ -0,0 +1,12 @@
+// "Wrap with '?.let { ... }' call" "true"
+// WITH_RUNTIME
+
+interface A
+
+operator fun A?.plus(a: A?): A? = this
+
+fun test(a1: A, a2: A) {
+    (a1 + a2<caret>)?.let { notNull(it) }
+}
+
+fun notNull(t: A): A = t