check-flagged-apis: api-versions.xml: correctly parse nested class ctor

The constructor of a nested class is represented as follows in
api-versions.xml:

  <class name="android/Clazz$Foo$Bar" since="1">
    <method name="&lt;init>()V"/>
  </class>

The nested dollar signs are not replaced by forward slashes before the
parsing logic uses `split("/")` to find the name of the inner-most
class, incorrectly resulting in `Class$Foo$Bar` instead of `Bar`. Fix
this by immediately replacing dollar signs with forward slashes after
extracting the package and class.

Also clean up the following call of `Symbol.create`.

Bug: 334870672
Test: atest --host check-flagged-apis-test
Change-Id: I8c0619faae90ded7eb14dcc20ecb94a086a1c764

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

@@ -139,6 +139,27 @@ class CheckFlaggedApisTest {
     assertEquals(expected, actual)
   }
 
+  @Test
+  fun testParseApiVersionsNestedClasses() {
+    val apiVersions =
+        """
+          <?xml version="1.0" encoding="utf-8"?>
+          <api version="3">
+            <class name="android/Clazz${'$'}Foo${'$'}Bar" since="1">
+              <method name="&lt;init>()V"/>
+            </class>
+          </api>
+        """
+            .trim()
+    val expected: Set<Symbol> =
+        setOf(
+            Symbol("android/Clazz/Foo/Bar"),
+            Symbol("android/Clazz/Foo/Bar/Bar()"),
+        )
+    val actual = parseApiVersions(apiVersions.byteInputStream())
+    assertEquals(expected, actual)
+  }
+
   @Test
   fun testFindErrorsNoErrors() {
     val expected = setOf<ApiError>()

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

@@ -279,12 +279,13 @@ internal fun parseApiVersions(input: InputStream): Set<Symbol> {
     var (methodName, methodArgs, _) = methodSignatureParts
     val packageAndClassName =
         requireNotNull(method.getParentNode()?.getAttribute("name")) {
-          "Bad XML: top level <method> element, or <class> element missing name attribute"
-        }
+              "Bad XML: top level <method> element, or <class> element missing name attribute"
+            }
+            .replace("$", "/")
     if (methodName == "<init>") {
       methodName = packageAndClassName.split("/").last()
     }
-    output.add(Symbol.create("${packageAndClassName.replace("/", ".")}.$methodName($methodArgs)"))
+    output.add(Symbol.create("$packageAndClassName/$methodName($methodArgs)"))
   }
 
   return output