* Test singular fields are encoded in canonical way
* Defautl values in proto3 should not be encoded.
* Values should be converted to the canonical representation (e.g.,
long int64 value may be truncated for int32 field)
* Update failure list
* Update failure list
* Add conformance tests for explicit packed/unpacked fields
* Fix typo
* Update failure lists
* Update failure list
* Use enum class to make enum scoped
* Add binary conformance test for default repeated fields
1) Both packed and unpacked encoding should be accepted for parsing.
2) Encode should follow the default way for the syntax.
* Uncomment test
* Remove is_primitive
* Add failed tests to failure lists.
* Add failed test to failure list
* Use binary format to specify expected value
Text format cannot distinguish whether repeated field is packed or not.
* Change method name from ToHexString to ToOctString
* Add failed test to failure list
* Add failed test to php's failure list
* Fix comments
* Add binary conformance test for message type.
* Add test case for merge repeated scalar message field
* Add failed tests to failure list
* Add failed test to php's failure list
* Remove successful tests from php c's failure list
* Add conformance test for nested listvalue
* Fix upb for parsing repeated Value/ListValue
* Add failed repeated ListValue conformance test into php failure list
