csv file fixtures

[emmyoop]

resolves #8290

Problem

No support for csv files in unit testing.

Solution

Support a csv file in addition to an inline csv definition.

  - name: test_my_model_empty
    model: my_model
    given:
      - input: ref('my_model_a')
        format: csv
        fixture: test_my_model_a_empty_fixture_csv
      - input: ref('my_model_b')
        format: csv
        fixture: test_my_model_fixture

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX
• This PR includes type annotations for new and modified functions

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (f629baa) 64.65% compared to head (07267a5) 86.67%.
Report is 9 commits behind head on unit_testing_feature_branch.

Additional details and impacted files

@@                       Coverage Diff                        @@
##           unit_testing_feature_branch    #9044       +/-   ##
================================================================
+ Coverage                        64.65%   86.67%   +22.02%     
================================================================
  Files                              181      181               
  Lines                            26973    27033       +60     
================================================================
+ Hits                             17440    23432     +5992     
+ Misses                            9533     3601     -5932     

Flag	Coverage Δ
integration	83.57% <95.12%> (?)
unit	64.59% <34.14%> (-0.06%)	⬇️

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

Files	Coverage Δ
core/dbt/config/project.py	97.47% <100.00%> (+7.18%)	⬆️
core/dbt/parser/unit_tests.py	93.45% <ø> (+40.18%)	⬆️
core/dbt/contracts/graph/unparsed.py	94.20% <94.28%> (+7.43%)	⬆️

... and 120 files with indirect coverage changes

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[gshank]

Looks good!