Minimal emulator implementation inside integration

[bluesign]

This adds a minimal emulator implementation inside integration to remove need for flow-emulator

• PoC in this commit range
• Addressing lint errors (mainly goimports and mod file tidying) in this commit range

Todos for @jordanschalm

• [x] Add package godoc for emulator package
• [x] Rename emulator package to avoid confusion with existing emulator, or move to internal package

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 54.76190% with 1121 lines in your changes missing coverage. Please review.

Project coverage is 41.29%. Comparing base (1d55978) to head (d6fe283). Report is 105 commits behind head on master.

Files with missing lines	Patch %	Lines
integration/internal/emulator/mocks/emulator.go	0.00%	257 Missing :warning:
integration/internal/emulator/blockchain.go	70.53%	166 Missing and 47 partials :warning:
...gration/internal/emulator/mocks/emulatorStorage.go	0.00%	171 Missing :warning:
integration/internal/emulator/sdk.go	50.15%	140 Missing and 26 partials :warning:
integration/internal/emulator/memstore.go	69.33%	55 Missing and 14 partials :warning:
integration/internal/emulator/errors.go	16.90%	59 Missing :warning:
integration/internal/emulator/convert.go	78.03%	48 Missing and 8 partials :warning:
integration/internal/emulator/config.go	55.37%	52 Missing and 2 partials :warning:
integration/internal/emulator/ledger.go	72.63%	18 Missing and 8 partials :warning:
integration/internal/emulator/emulator.go	40.54%	21 Missing and 1 partial :warning:
... and 3 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6594      +/-   ##
==========================================
+ Coverage   41.16%   41.29%   +0.13%     
==========================================
  Files        2031     2050      +19     
  Lines      179463   182574    +3111     
==========================================
+ Hits        73869    75400    +1531     
- Misses      99381   100847    +1466     
- Partials     6213     6327     +114     

Flag	Coverage Δ
unittests	41.29% <54.76%> (+0.13%)	:arrow_up:

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