We are proposing to increase the number of active collators in the ecosystem to 35 and to allow for smaller holders to be part of securing the Kilt network.

Set the maximum number of collator candidates that can be selected
at the beginning of each validation round.

Changes are not applied until the start of the next round.

The new value must be higher than the minimum allowed as set in the
pallet's configuration.

The dispatch origin must be Root.

Emits `MaxSelectedCandidatesSet`.


# <weight>
- The transaction's complexity is mainly dependent on updating the
  `SelectedCandidates` storage in `select_top_candidates` which in
  return depends on the number of `MaxSelectedCandidates` (N).
- For each N, we read `CandidatePool` from the storage.
---------
Weight: O(N + D) where N is `MaxSelectedCandidates` bounded by
`MaxTopCandidates` and D is the number of delegators of a
candidate bounded by `MaxDelegatorsPerCollator`.
- Reads: MaxSelectedCandidates, TopCandidates, N * CandidatePool
- Writes: MaxSelectedCandidates
# </weight>



1. Proposing an increase of active collators in ecosystem to 35. 
2. Opportunity to make network more secure by allowing smaller holders to take part in Kilt network.

#20 This proposal is to increase the active number of collators to 35