Change QuicHttpIntegrationTest to use TestUsingSimulatedTime

`QuicHttpIntegrationTest` sometimes flakes, especially lately in the [AsyncCertVerificationAfterDisconnect](https://github.com/envoyproxy/envoy/blob/90068a6eb1739ffcef555f793cce27220ab43120/test/integration/quic_http_integration_test.cc#L725) and [AsyncCertVerificationAfterTearDown](https://github.com/envoyproxy/envoy/blob/90068a6eb1739ffcef555f793cce27220ab43120/test/integration/quic_http_integration_test.cc#L768) tests, which depend on timing of the QUIC disconnects and completion of cert verification.

We've addressed the issue by adjusting the timeouts: https://github.com/envoyproxy/envoy/pull/38864

However, a better long term solution would be to use a simulated time system for the test: [TestUsingSimulatedTime](https://github.com/envoyproxy/envoy/blob/a8f78e6c120decd989477a215350a6c419c2fb55/test/test_common/simulated_time_system.h#L133)