Add bound to the number of venue_signers

[HenriqueNogara]

Adds a bound to the number of venue_signers.

changelog

modified API

• Adds the NumberOfVenueSignersExceeded variant to the settlement error enum;

modified logic

• Returns an error if the the number of venue signers exceed the maximum;

[codecov[bot]]

Codecov Report

Merging #1521 (6175f15) into develop (f73344d) will increase coverage by 0.01%. The diff coverage is 65.38%.

@@             Coverage Diff             @@
##           develop    #1521      +/-   ##
===========================================
+ Coverage    58.45%   58.46%   +0.01%     
===========================================
  Files          142      142              
  Lines        31399    31415      +16     
===========================================
+ Hits         18353    18368      +15     
- Misses       13046    13047       +1     

Files Changed	Coverage Δ
pallets/runtime/common/src/runtime.rs	1.81% <ø> (ø)
pallets/runtime/develop/src/runtime.rs	3.65% <ø> (ø)
pallets/settlement/src/lib.rs	76.84% <65.38%> (+0.29%)	:arrow_up:

... and 3 files with indirect coverage changes