fix #11577: have checksum provider list available hashers (rebased onto dev_5_0)



This is the same as gh-1915 but rebased onto dev_5_0.

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This should remove a client call to the server on import, while making the client robust against the server preferring a hasher that the client does not implement.

To test, make sure that import still works, still writing appropriate values for `hasher`, `hash` into the `originalfile` table; perhaps also experiment with setting `omero.checksum.supported` in `etc/omero.properties`.

Fixes https://trac.openmicroscopy.org.uk/ome/ticket/11577.
--no-rebase as 5.x-specific.