Another shot at tool shed API fixes

[jmchilton]

Longer term we've got get away from the ugly global data and invalid multi-threading of the hgweb_config_manager global instance of HgWebConfigManager.

If this fixes #18556 this time - we could replace all our repo_path calculation to skip that object using this mechanism and then... have one process that deals with keeping the hg web stuff in sync and just communicate with it using tasks? I really want Celery on the tool shed servers but I know our admin resources for the tool sheds are already tapped out 😿.

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