What problem does this solve or what need does it fill?

Following #15276 we should expose new system params that benefit from no panics.
Specifically, we should support entities that act as resources.
We can provide system parameters that are equivalents of Query::single family of methods.

What solution would you like?

Add the following system parameters:

• QuerySingle<Q, F> - valid with exactly one result
• Option<QuerySingle<Q, F>> - valid with zero or one result