Merge 3.20.1-rc1 into main (#9760)

* Fix NPE during encoding and add regression test for issue 9507.

(cherry picked from commit 58e320a7323b55f65137222064ed0e72fe423e23)

* Implement `respond_to?` in RubyMessage (#9677)

All synthetic methods implemented by `method_missing` are now supported by `respond_to?`.

Fixes issue #9202.

* Fix null pointer exceptions exposed by new regression tests.
* Fix clear_ on oneofs so that it is safe to call repeatedly and so that respond_to? does not depend on whether the oneof is currently cleared.
* Code cleanup: reenable more tests on JRuby.
* Align JRuby behavior with CRuby by throwing a RuntimeError when attempting to assign to a oneof.

(cherry picked from commit 8e7f93669612a06cafc39625f61258b9d6b77a3c)

* Update protobuf version

* Merge pull request #9727 from mlocati/build-packaged-php-extension

Fix building packaged PHP extension

(cherry picked from commit 7f9901c5f640fe0fbcd5dbdd303a269908fb3b62)

* Update protobuf version

* Update changelogs for 3.20.1-rc1

Co-authored-by: Jason Lunn <jason.lunn@gmail.com>
Co-authored-by: Jorg Brown <jorg.brown@gmail.com>

Author: 3 people

package.json

@@ -1,6 +1,6 @@
 {
   "name": "google-protobuf",
-  "version": "3.20.0",
+  "version": "3.20.1-rc.1",
   "description": "Protocol Buffers for JavaScript",
   "main": "google-protobuf.js",
   "files": [