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}
(cherry picked from commit 58f0aa68fb0a15b0af56e7cfdf833ac3108fa00e)

TBR=rch@chromium.org,bengr@chromium.org

Review URL: https://codereview.chromium.org/2019933002 .

Cr-Commit-Position: refs/branch-heads/2743@{#120}
Cr-Branched-From: 2b3ae3b8090361f8af5a611712fc1a5ab2de53cb-refs/heads/master@{#394939}
10 files changed