GEP: Review Percentage-based request mirroring GEP

[kate-osborn]

A/C:

• Review Adding GEP 3171: Percentage-based Request Mirroring kubernetes-sigs/gateway-api#3178
• Determine if NGF can support proposed API
• Contribute to the conversation as to NGF's stance on the API
• Review summary with the team.

[sjberman]

NGF can support this using split_clients to set percentages