refactor(AccountId): underlying representation to be Address32

[failfmi]

Detailed description:

Which issue(s) this PR fixes:
Fixes #300

Special notes for your reviewer:

Checklist

• Documentation added
• Tests updated

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (f4937b4) 78.08% compared to head (557209b) 78.25%.

❗ Current head 557209b differs from pull request most recent head d762866. Consider uploading reports for the commit d762866 to get more accurate results

Files	Patch %	Lines
primitives/types/lookup.go	70.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #305      +/-   ##
===========================================
+ Coverage    78.08%   78.25%   +0.16%     
===========================================
  Files          157      157              
  Lines        10431    10424       -7     
===========================================
+ Hits          8145     8157      +12     
+ Misses        1914     1899      -15     
+ Partials       372      368       -4     

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