PlzNavigate: move FYI bot test exclusion filters into files.

Following in the lines of what has been recently done to the Site
Isolation bots this change moves the test exclusion filters from the bot
definition JSON file to exclusive files. This will ease updating the
filters by eliminating the need of the JSON file owner approval.

BUG=563624

Review URL: https://codereview.chromium.org/1565753002

Cr-Commit-Position: refs/heads/master@{#368103}