SNMP RFC amendments and clarification

Hello internals, The following RFC https://wiki.php.net/rfc/snmp_improvements_2026 stipulated that the proposed PHP versions for this RFC are: "Next stable release for all currently supported PHP versions." This goes against our policy regarding versioning (https://github.com/php/policies/blob/main/release-process.rst#patch-version-number). As such these changes will *only* land in PHP 8.6. Moreover, I suggested replacing the new integer constants for the "Implement more MIB parsing and value output controls" part of the RFC by PHP enums to improve type safety from the userland perspective. I think this is an improvement on multiple levels as it also effectively "translates" the C enums defined by SNMP to PHP enums exposed to userland. The plan is to have this merged in time for PHP 8.6.0beta2 so people can test this. Best regards, Gina P. Banyard