Missing reducers

[nliber]

While writing the documentation to address kokkos/kokkos#8097, we are missing documentation for the following reducers:

MaxFirstLoc
MaxFirstLocCustomComparator
MinFirstLoc
MinFirstLocCustomComparator
MinMaxFirstLastLoc
MinMaxFirstLastLocCustomComparator
FirstLoc
LastLoc
StdIsPartitioned
StdPartitionPoint

[nliber]

Not sure yet if I'll address this with a separate PR to address kokkos/kokkos#8097 or do it all as one.