jni_generator: Refactor parsing logic

The main changes are:
* Moves parsing of .java files into "parse.py"
  * Parsing of javap remains in jni_generator.py for now.
* Introduces a "JavaClass" class, to model class references
* Moves ProxyHelpers into a separate "proxy.py" file.
* Makes JNIFromJavaP and JNIFromJavaSource both have a "GetContent()",
  which simplifies main() logic a bit.
* Teaches TypeResolver about importing nesting classes

Bug: 1406605
Change-Id: I99d2efe02353967191ef09ce0b8a7dea5737d44d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4545780
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Peter Wen <wnwen@chromium.org>
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1146645}

base/android/jni_generator/common.py

@@ -0,0 +1,10 @@
+# Copyright 2023 The Chromium Authors
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+"""Common logic needed by other modules."""
+
+
+def EscapeClassName(fully_qualified_class):
+  """Returns an escaped string concatenating the Java package and class."""
+  escaped = fully_qualified_class.replace('_', '_1')
+  return escaped.replace('/', '_').replace('$', '_00024')

base/android/jni_generator/java/src/org/chromium/example/jni_generator/SampleProxyEdgeCases.java

@@ -6,6 +6,7 @@
 
 import org.chromium.example.jni_generator.Boolean;
 
+@SomeAnnotation("that contains class Foo ")
 class SampleProxyEdgeCases {
     enum Integer {}