Change KeyPair type from int to Hash

[tomek0123456789]

Closes #1153

Introduced changes

• KeyPair constructor accepts Hash type
• KeyPair.from_private_key accepts Hash type

• This PR contains breaking changes

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.21% 🎉

Comparison is base (0243f05) 96.99% compared to head (abede2e) 97.20%.

Additional details and impacted files

@@               Coverage Diff               @@
##           development    #1157      +/-   ##
===============================================
+ Coverage        96.99%   97.20%   +0.21%     
===============================================
  Files               92       92              
  Lines             4419     4433      +14     
===============================================
+ Hits              4286     4309      +23     
+ Misses             133      124       -9     

Files Changed	Coverage Δ
starknet_py/net/signer/stark_curve_signer.py	100.00% <100.00%> (ø)
starknet_py/net/signer/test_stark_curve_signer.py	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes

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