2022-03-25 version 3.20.0 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)

C++

Add option to use external GTest in CMake (#8736)
cmake: Set correct sonames for libprotobuf-lite.so and libprotoc.so (#8635) (#9529)

Java

Dropped Ruby 2.3 and 2.4 support for CI and releases. (#9311)
[Ruby] Message.decode/encode: Add max_recursion_depth option (#9218)
Ruby: rename max_recursion_depth to recursion_limit (#9486)
Fix conversion of singleton classes in Ruby (#9342)
Suppress warning for intentional circular require (#9556)
[Ruby] allow encode json options to be an object that responds to to_hash (#9513)

[C#] Fix trim warnings (#9182)
Add protoc-gen-go-svc to options.md (#9280)
Fixes NullReferenceException when accessing FieldDescriptor.IsPacked (#9430)
Add ToProto() method to all C# descriptor classes (#9426)
Add cmake option protobuf_INSTALL to not install files (#7123)
[CMake] Allow custom plugin options e.g. to generate mocks (#9105)
Add an option to preserve proto names in JsonFormatter (#6307)
Add test scope to kotlin-test for protobuf-kotlin-lite (#9518)
Add prefix_to_proto_package_mappings_path ObjC option. (#9498)
[ObjC] Rename proto_package_to_prefix_mappings_path to package_to_prefix_mappings_path. (#9552)
cmake: Use linker version scripts (#9545)
Add a generation option to control use of forward declarations in headers. (#9568)
[C#] fix parse failure for extensions with large field numbers (#9591)