[IP Protection] Add proxy chain and is-proxy-session to QuicSessionKey

Updates QuicSessionKey to include a ProxyChain and an IsProxySession
member, mirroring what's done for SpdySessionKey. This means that a
tunnel established through a proxy chain will no longer share a QUIC
session with a connection established directly to the proxy. A new
QuicNetworkTransactionTest test is added for this. This change also
gets us closer to supporting multi-proxy chains for cases like where
a tunnel is established through the same proxy server twice.

Also, this CL removes the use_dns_aliases parameter from
QuicSessionRequest::Request, since this can be calculated from the
new IsProxySession parameter, and also removes
QuicSessionPoolPeer::HasLiveSession since it is unused.

Change-Id: Ieb5edee570508f9774914d2d7c69d8bb617e57b4
Bug: 1491092, 1495793
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5205530
Reviewed-by: Dustin Mitchell <djmitche@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Andrew Williams <awillia@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1251058}

• net/BUILD.gn[diff]
• net/http/http_proxy_connect_job.cc[diff]
• net/http/http_stream_factory_job.cc[diff]
• net/http/http_stream_factory_job.h[diff]
• net/http/http_stream_factory_job_controller.cc[diff]
• net/http/http_stream_factory_job_controller_unittest.cc[diff]
• net/quic/bidirectional_stream_quic_impl_unittest.cc[diff]
• net/quic/quic_chromium_client_session_peer.cc[diff]
• net/quic/quic_chromium_client_session_test.cc[diff]
• net/quic/quic_http_stream_test.cc[diff]
• net/quic/quic_network_transaction_unittest.cc[diff]
• net/quic/quic_proxy_client_socket_unittest.cc[diff]
• net/quic/quic_session_key.cc[diff]
• net/quic/quic_session_key.h[diff]
• net/quic/quic_session_key_unittest.cc[Added - diff]
• net/quic/quic_session_pool.cc[diff]
• net/quic/quic_session_pool.h[diff]
• net/quic/quic_session_pool_fuzzer.cc[diff]
• net/quic/quic_session_pool_peer.cc[diff]
• net/quic/quic_session_pool_peer.h[diff]
• net/quic/quic_session_pool_test.cc[diff]
• net/websockets/websocket_basic_stream_adapters_test.cc[diff]
• net/websockets/websocket_handshake_stream_create_helper_test.cc[diff]