[Access] Improve logging and validation in local script exec

[peterargue]

Closes: #4919
Closes: #4918

This PR includes 3 fixes:

1. Add validation for address to GetAccount. This was missing from this endpoint, but existed for other GetAccount* endpoints.
2. Improve error comparison for semantically identical script execution errors
3. Return InvalidArgument errors from AccessAPI handler when request contained invalid flow.Identifier

[codecov-commenter]

Codecov Report

Attention: 11 lines in your changes are missing coverage. Please review.

Comparison is base (3704b14) 52.97% compared to head (1de1e25) 57.16%.
Report is 16 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4920      +/-   ##
==========================================
+ Coverage   52.97%   57.16%   +4.18%     
==========================================
  Files         754      785      +31     
  Lines       68131    74061    +5930     
==========================================
+ Hits        36095    42335    +6240     
+ Misses      29316    28512     -804     
- Partials     2720     3214     +494     

Flag	Coverage Δ
unittests	57.16% <0.00%> (+4.18%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
engine/access/rpc/backend/backend_scripts.go	71.18% <0.00%> (ø)

... and 370 files with indirect coverage changes

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[Guitarheroua]

Looks good for me.