MESH-2111 improve multisig storage all

[Neopallium]

changelog

modified API

• Change multisig.Proposals to a double map (ms -> proposal id -> proposal).
• Change multisig.ProposalDetail to a double map (ms -> proposal id -> proposal_detail).
• Change multisig.Votes to a double map ((ms, proposal id) -> signer -> bool).

[codecov[bot]]

Codecov Report

Merging #1543 (02d3add) into develop (03cd84f) will increase coverage by 0.01%. The diff coverage is 51.72%.

@@             Coverage Diff             @@
##           develop    #1543      +/-   ##
===========================================
+ Coverage    58.66%   58.67%   +0.01%     
===========================================
  Files          142      142              
  Lines        31873    31879       +6     
===========================================
+ Hits         18698    18705       +7     
+ Misses       13175    13174       -1     

Files	Coverage Δ
pallets/multisig/src/lib.rs	85.26% <51.72%> (-1.00%)	:arrow_down:

... and 3 files with indirect coverage changes