neofs-adm: fixes for contract update

[fyrchik]

1. Compare NEF.Checksum to check if contract is updated.
2. Replace addRoot with register in NNS.
3. Compare hashes written to NNS properly.

[codecov]

Codecov Report

Merging #984 (134bd19) into master (011d0f6) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #984      +/-   ##
==========================================
- Coverage   38.31%   38.27%   -0.05%     
==========================================
  Files         258      258              
  Lines       13504    13519      +15     
==========================================
  Hits         5174     5174              
- Misses       7898     7913      +15     
  Partials      432      432              

Impacted Files	Coverage Δ
...fs-adm/internal/modules/morph/initialize_deploy.go	0.00% <0.00%> (ø)
...neofs-adm/internal/modules/morph/initialize_nns.go	0.00% <0.00%> (ø)

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[alexvanin]

Add [#984] to commit header.