Replace ProxyConfigSource with ProxyConfigWithAnnotation.

ProxyConfigSource is removed and ProxyConfigWithAnnotation class is
added to wrap a constant ProxyConfig and its NetworkTrafficAnnotation.
To goal is to provide an annotation wherever a ProxyConfig is modified,
so that the source of configs for proxies and their changes would be
traceable and transparent.

Bug: 656607
Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester;master.tryserver.chromium.linux:linux_mojo;master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I64f0eaad8f37682da4571b4a9aae69d974ce584d
Reviewed-on: https://chromium-review.googlesource.com/934126
Commit-Queue: Ramin Halavati <[email protected]>
Reviewed-by: Jochen Eisinger <[email protected]>
Reviewed-by: Daniel Cheng <[email protected]>
Reviewed-by: Helen Li <[email protected]>
Reviewed-by: Eric Roman <[email protected]>
Cr-Commit-Position: refs/heads/master@{#542426}
105 files changed