Apply Status to SnippetsFilter Resources

[mpstefan]

As a user of NGF
I want my SnippetsFilter resource status to be updated when NGF detects to it
So that I know if my SnippetsFilter is valid and if it was applied.

Acceptance

• If the SnippetsFilter resource on the graph is valid, then NGF will write an "Accepted" condition with a "true" value to status with a reason of "Accepted."
• If the SnippetsFilter resource on the graph is invalid, then NGF will write an "Accepted" condition with a "false" value to status with a reason of "Invalid."
• If the Accepted condition is false, the message and condition should describe why the resource is invalid.

Dev Notes

• Design: https://github.com/nginxinc/nginx-gateway-fabric/blob/main/docs/proposals/advanced-nginx-extensions.md#api