Return cookies from other watches or watchmen

Summary:
For certain uses of watchman it is important for its view of the file system to be as consistent as possible. So instead of hiding all cookie files altogether, show cookie files
created by other watchman processes or by other watches for the same process.

Test Plan: `arc unit --everything`. Also ran `tests/integration/othercookies.php` against master and saw that it failed.

Reviewers: wez

Reviewed By: wez

Differential Revision: https://phabricator.fb.com/D898053

Task ID: 2646666

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extra : rebase_source : 68d2ae494ea6d81dd265d47dbebf488cf04e5057
extra : amend_source : df532925ce0bd6ca5d442780448e46288c8a9655