Change secp256k1 and test library

[kigawas]

Closes #696

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (8902d54) 100.00% compared to head (6f3d62e) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #720   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          101       169   +68     
  Branches        12        47   +35     
=========================================
+ Hits           101       169   +68     

Impacted Files	Coverage Δ
src/consts.ts	100.00% <100.00%> (ø)
src/index.ts	100.00% <100.00%> (ø)
src/keys/PrivateKey.ts	100.00% <100.00%> (ø)
src/keys/PublicKey.ts	100.00% <100.00%> (ø)
src/utils.ts	100.00% <100.00%> (ø)

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[paulmillr]

futoin-hkdf can also be replaced with @noble/hashes/hkdf