Support regular-expression paths in RestApi operations

Description

The gateway-controller's RestApi Operation.Path (api.yaml) supports only three path forms — an exact path, the /* wildcard prefix, and {param} single-segment placeholders (gateway/gateway-controller/pkg/xds/translator.go).
Literal portions are regexp.QuoteMeta-escaped before being compiled to an Envoy SafeRegex, so any regex metacharacters a user puts in a path are matched literally — there is no way to define an arbitrary regular-expression path.

This also limits the Gateway API operator flow: a HTTPRoute match of type: RegularExpression has no faithful RestApi equivalent, so the operator rejects it with an Invalid config error (see #2021 and PR #2066).

Adding first-class regex path support to the RestApi YAML would let users define regex-based operation paths directly, and would unblock the operator mapping HTTPRoute RegularExpression matches instead of rejecting them.

Possible approach: introduce an explicit path-match type on the operation (e.g. pathType: exact | prefix | regex, or a dedicated pathRegex field) so the controller emits a SafeRegex route from a user-provided pattern, with validation that rejects invalid or unsafe (e.g. catastrophic-backtracking) patterns.

Version

No response

Related Issue

#2021, #2066

Start with gateway/gateway-controller/pkg/xds/translator.go and the RestApi Operation definition in api.yaml to understand the existing exact, prefix, and parameter path handling. Review #2021 and PR #2066 for the Gateway API operator requirements. Done means RestApi can represent a validated regular-expression path and the operator can map HTTPRoute RegularExpression matches without rejecting them.