Fix for CVE-2022-3509 and CVE-2022-3510 in v2.5.0

[mohdiliyaj]

Hello,

I am working on addressing the vulnerabilities CVE-2022-3509 and CVE-2022-3510 in Protobuf version v2.5.0. I understand that these issues were resolved in version v3.16.3, but since there are significant code changes between v2.5.0 and v3.16.3, I have backported the fixes specifically to v2.5.0.

Could you please review the mohdiliyaj@634c0d0 commit and confirm whether it sufficiently addresses both vulnerabilities?

Thank you