check-flagged-apis: skip self-referential interfaces

The return value of ClassItem.allInterfaces will sometimes include the
interface itself (e.g.
android.accessibilityservice.BrailleDisplayController). It is unclear
when this happens; it doesn't happen for the unit test.

Update the logic to record the interfaces for a class to filter out
interfaces named the same as the class.

Bug: 334870672
Test: atest --host check-flagged-apis-test
Test: croot && ./build/tools/check-flagged-apis/check-flagged-apis.sh
Change-Id: I8d93c230dfedde30e8d43fefd560a47944085d3a

tools/check-flagged-apis/src/com/android/checkflaggedapis/Main.kt

@@ -198,7 +198,10 @@ internal fun parseApiSignature(path: String, input: InputStream): Set<Pair<Symbo
             val symbol =
                 Symbol.createClass(
                     cls.baselineElementId(),
-                    cls.allInterfaces().map { it.baselineElementId() }.toSet())
+                    cls.allInterfaces()
+                        .map { it.baselineElementId() }
+                        .filter { it != cls.baselineElementId() }
+                        .toSet())
             output.add(Pair(symbol, flag))
           }
         }