ReplacePrefixMatch in the URLRewrite filter does not handle empty match prefix correctly

[sadovnikov]

Description:

In its examples, the Gateway API uses "foo" in "Prefix Match". However, we can conclude that the HTTPPathModifier should also work on / as the path prefix match.

The PR #5254 PR demonstrates that / is not handled correctly.

Repro steps:

Follow the end-2-end test, which is added in #5254

Environment:

In our environment, we use docker.io/envoyproxy/gateway:v1.3.0. The bug is reproducible in the main branch, and is reproducible in v1.2.5

[arkodg]

relates to kubernetes-sigs/gateway-api#3592

we've had some issues in this area

• ReplacePrefixMatch not working  #2976
• Incorrect url rewrite, double slash #3807
• replacePrefixMatch broken in main #4331

hoping someone can help with ironing this out

[arkodg]

cc @zhaohuabing @LiorLieberman

[LiorLieberman]

Are we good to employ istio/istio#54939?

Will also start a discussion in slack