Implement multiple alternative services per origin.

HttpServerProperties:
 * Introduce AlternativeServiceVector and AlternativeServiceInfoVector.
 * Change AlternativeServiceMap typedef.

HttpServerPropertiesImpl:
 * Add bool SetAlternativeServices.
 * Change SetAlternativeService return type to bool.
 * Replace GetAlternativeService with GetAlternativeServices.
 * Replace ClearAlternativeService with ClearAlternativeServices.

HttpServerPropertiesManager:
 * Implement saving and loading preferences to support multiple alternative
   services per origin.

HttpStreamFactory and QuicStreamFactory:
 * Use first alternative service for now; more work to be done here.

Also update misc clients and add and update unittests.

BUG=392575

Review URL: https://codereview.chromium.org/1216703002

Cr-Commit-Position: refs/heads/master@{#337772}
13 files changed