[Cronet] Replace setExperimentalQuicConnectionOptions with a more general API

This CL replaces CronetEngine.Builder#setExperimentalQuicConnectionOptions with
a more general API to set experimental options.

BUG=545118

NOTRY=true
NOPRESUBMIT=true

Review URL: https://codereview.chromium.org/1414053008

Cr-Commit-Position: refs/heads/master@{#360187}
(cherry picked from commit 61b1eaaab7d5f38c76a3fd41d23a737fe177d211)

Review URL: https://codereview.chromium.org/1487723002

Cr-Commit-Position: refs/branch-heads/2564@{#160}
Cr-Branched-From: 1283eca15bd9f772387f75241576cde7bdec7f54-refs/heads/master@{#359700}
5 files changed