Enable AltSvc pooling by default.

* Change enable_alternative_service_with_different_host default value to true in
  production.
* Change enable_alternative_service_with_different_host default value to true in
  tests.
* Remove kEnableAlternativeServices command line switch.
* Change QUIC field trial parameter "enable_alternative_service_with_different_host"
  behavior from enabling if true to disabling if value is false.

BUG=392575

Review-Url: https://codereview.chromium.org/1986633002
Cr-Commit-Position: refs/heads/master@{#396508}
9 files changed