mgr/dashboard: Add clay plugin support

mgr/dashboard: Add clay plugin support

The erasure code plugin "clay" is now supported by the dashboard. Now a
clay based profile can be created in the ec profile creation modal
dialog which can be found in the pool form.

The defaults of the plugin are calculated or preselected and shown in the
dashboard, therefore things are made mandatory even if they are not on the
cli, but as they automatically set the user doesn't have to set them,
but sees the defaults instantly before creating the profile.
(This is the same behavior that is used for all other supported
plugins.)

Fixes: https://tracker.ceph.com/issues/44433
Signed-off-by: Stephan Müller <smueller@suse.com>