Android: turn on auto-detect encoding by default

Now that CED (Compact Encoding Detection) library replaced
ICU (crrev.com/2081653007), turning on auto-detect encoding
by default became feasible without regression on page
loading time. Also removed the encoding menu in site
setting (originally added in crrev.com/1248163002).

Will remove the menu on the other platforms in a follow-up
CL.

BUG=597488

Review-Url: https://codereview.chromium.org/1894913002
Cr-Commit-Position: refs/heads/master@{#407005}
67 files changed