docs: fix ambient waypoint tests by consolidating into e2e test

The ambient waypoint documentation tests were failing in CI because
they were split into 9 separate test blocks that each assumed Istio
ambient mode, IstioCNI, ZTunnel, and bookinfo were already set up.

This commit replaces the 9 individual test blocks with a single
comprehensive end-to-end test that includes:

- Phase 1: Prerequisites and Setup (Gateway API, namespaces, Istio,
  IstioCNI, ZTunnel, bookinfo application)
- Phase 2: Waypoint Proxy Testing (deployment, enrollment, verification)
- Phase 3: L7 Features Testing (HTTPRoute, AuthorizationPolicy)
- Phase 4: Cleanup (complete removal of all resources)

The new test is self-contained and includes all required prerequisites,
ensuring it can run successfully in the docs-test CI job.

Fixes: CI docs-test failure
Related: commit 6a77ef5 (docs: add ifdef blocks for waypoint proxy doc tests)

Signed-off-by: Rafael Zago <[email protected]>

Author: rafaelvzago