mgr/dashboard: ECP modal enhanced validation

mgr/dashboard: ECP modal enhanced validation

New validations with meaningful error messages:
* For all plugins
  * k + m <= OSDs that are available
  * k > 1
* For LRC
  * Display calculation factor for k (always)
  * Show error calculation for k is not met (also shows calculation)
  * Display number of groups for l (always)
  * Show error if calculation for l is not met (also shows calculation)
* For SHEC
  * m <= k
  * c <= m

Fixes: https://tracker.ceph.com/issues/44621
Signed-off-by: Stephan Müller <smueller@suse.com>