PHP namespaces for nested messages and enums (#4536)

* uses namespaces for nested messages and enums

* fixes namespaces for PHP dist

* fixes namespace for Descriptors, adds Cardinality and Kind

* fixes nested namespaces for reserved words and adds tests

* adds tests and generator fix for php class prefixes

* fixes escaping of protobuf packages, enum comments, misc others

* nice refactor of generated code

* adds class files for backwards compatibility

* simplifies code with templates

* adds compatibility files to makefile

* cleanup of generator and fixes nested namespace bug

* regenerates proto types

* remove internal BC classes

* adds deprecated warning, adds methods back

* simplifies if statement

* fixes dist files

* addresses review comments

* adds back TYPE_URL_PREFIX constant

* adds @deprecated to old nested class files

* skips tests which require a separate process when protobuf.so is enabled

* Adds tests for legacy nested classes that do not require separate processes to test

* uses legacy names for GPBUtil message check

* adds block for IDE @deprecated message

* Namespace for nested message/enum in c extension

* Remove unused code

1 files changed, 8 insertions, 4 deletions

diff --git a/php/tests/proto/test_no_namespace.proto b/php/tests/proto/test_no_namespace.proto
index 03f89270..cce42ea2 100644
--- a/php/tests/proto/test_no_namespace.proto
+++ b/php/tests/proto/test_no_namespace.proto
@@ -5,11 +5,15 @@ option php_metadata_namespace = "\\";
 message NoNamespaceMessage {
   int32 a = 1;
 
-  enum NestedEnum {
-    ZERO = 0;
+  // Test nested messages, enums, and reserved names
+  NestedMessage nested_message = 2;
+  NestedEnum nested_enum = 3;
+  message NestedMessage {
+    int32 a = 1;
   }
-  NestedEnum b = 2;
-  repeated NestedEnum c = 3;
+  enum NestedEnum {
+      ZERO = 0;
+  };
 }
 
 enum NoNamespaceEnum {