Now per-file inherits global owners by default.
Bug: 128838191
Test: upload validator and [FIND OWNERS]
Change-Id: I58fb3cc8f2f277a5aa4b3372734197d888e59bcc
* Owners are selected from top CL approvals or owners.
They will be suggested to review/approve future CLs.
* OWNERS files are recognized by the new find-owners plugin, see .md files in
https://gerrit.googlesource.com/plugins/find-owners/+/master/src/main/resources/Documentation/
Test: build/make/tools/checkowners.py -c -v OWNERS
Change-Id: Ibe6765e5448c471ca413413e3d052507ccee4ea6