Implement Leo Account

[collinc97]

leo account new #generates a new private key, view key, address
leo account new --write #generates a new private key, view key, address and saves to .env

leo account import APrivateKey1zkp... #imports view key and address from private key string
leo account import APrivateKey1zkp... --write #imports view key and address from private key string and saves to .env

[codecov]

Codecov Report

Merging #2513 (52be020) into testnet3 (d336be0) will increase coverage by 0.09%.
Report is 6 commits behind head on testnet3.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##           testnet3    #2513      +/-   ##
============================================
+ Coverage     78.93%   79.02%   +0.09%     
============================================
  Files           156      156              
  Lines          4942     4945       +3     
  Branches       4942     4945       +3     
============================================
+ Hits           3901     3908       +7     
+ Misses         1041     1037       -4     

Files Changed	Coverage Δ
errors/src/errors/mod.rs	23.52% <ø> (ø)
leo/package/src/package.rs	80.64% <ø> (ø)
compiler/compiler/tests/utilities/mod.rs	87.67% <100.00%> (-1.52%)	⬇️
leo/package/src/root/env.rs	94.44% <100.00%> (+1.11%)	⬆️

... and 14 files with indirect coverage changes

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[d0cd]

LGTM!