Extensions: Switch to new permission message system, part I
- Update lots of tests to check that the old and new system match.
- In the process, fix two small bugs in the new system.
- Rename PermissionsData::GetPermissionMessageStrings and GetPermissionMessageDetailsStrings to "*Legacy*", to match the corresponding methods in PermissionMessageProvider.
BUG=398257
TBR=asargent
for a trivial rename in ephemeral_app_launcher.cc
Review URL: https://codereview.chromium.org/
980353003
Cr-Commit-Position: refs/heads/master@{#321550}