Update polymesh-api and use manual settlement execution.

[Neopallium]

Update example settlement contract to use manual settlement execution.

[codecov[bot]]

Codecov Report

Merging #1391 (7808464) into develop (dd0c2af) will increase coverage by 0.07%. The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #1391      +/-   ##
===========================================
+ Coverage    43.28%   43.35%   +0.07%     
===========================================
  Files          140      140              
  Lines        30145    30145              
===========================================
+ Hits         13047    13069      +22     
+ Misses       17098    17076      -22     

Impacted Files	Coverage Δ
pallets/balances/src/lib.rs	57.10% <0.00%> (-0.14%)	:arrow_down:
primitives/src/asset_identifier.rs	98.34% <0.00%> (+0.41%)	:arrow_up:
pallets/settlement/src/lib.rs	47.05% <0.00%> (+1.62%)	:arrow_up: