feat(storage): Add CRC32c Checksums to Cloud Storage uploads. (#1846)
feat(storage): Add CRC32c Checksums to Cloud Storage uploads. (#1846)

* Add crc32 support

* Throw ServiceException instead of GoogleException

* Fix tests

* Provide either md5 or crc32c, update documentation and tests

* Autoselect signing method

* Test validation method

* Add link to extension source

* Bump crc32 version

* Address review comments

googleapis/google-cloud-php-core