rpc: add Rules signer scope to request parameters

[AnnaShaleva]

Port a part of neo-project/neo-modules#694. Waiting for the reference PR to settle.

[codecov]

Codecov Report

Merging #2384 (3d5b1d8) into master (992d74d) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2384      +/-   ##
==========================================
- Coverage   84.97%   84.96%   -0.01%     
==========================================
  Files         290      290              
  Lines       36050    36052       +2     
==========================================
+ Hits        30632    30633       +1     
- Misses       4119     4120       +1     
  Partials     1299     1299              

Impacted Files	Coverage Δ
pkg/core/blockchain.go	82.88% <100.00%> (ø)
pkg/core/dao/dao.go	83.13% <100.00%> (ø)
pkg/rpc/request/param.go	87.34% <100.00%> (+0.07%)	⬆️
pkg/network/server.go	74.08% <0.00%> (-0.10%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ff60571...3d5b1d8. Read the comment docs.

[roman-khimov]

This should be done irrespective of neo-project/neo-modules#694 outcome.