Features/repodata gateway (#12003)

* [WIP] repo: repodata interface

Signed-off-by: Filipe Laíns <lains@riseup.net>

* refactor subdir_data to use conda.gateways.repodata

* remove extra exception handling from subdir_data

* increment REPODATA_PICKLE_VERSION

* do not upload errors during test

* re-raise if not repodata.json

* consistent error handling in fetch_repodata_remote_request

Signed-off-by: Filipe Laíns <lains@riseup.net>
Co-authored-by: Filipe Laíns <lains@riseup.net>
Co-authored-by: Travis Hathaway <travis.j.hathaway@gmail.com>