Fix snapshot config to work in yaml files

[gshank]

resolves #4000

Problem

Validation that all required keys exist was being done when the snapshot sql file was being created, so it was not possible to define the config in a yaml file.

Solution

Delay part of the validation until the end of parsing.

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

All modified and coverable lines are covered by tests ✅

Project coverage is 87.94%. Comparing base (b680c7a) to head (c8ab084).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10275      +/-   ##
==========================================
- Coverage   88.73%   87.94%   -0.79%     
==========================================
  Files         180      180              
  Lines       22474    22495      +21     
==========================================
- Hits        19942    19783     -159     
- Misses       2532     2712     +180     

Flag	Coverage Δ
integration	84.55% <100.00%> (-1.54%)	⬇️
unit	63.21% <70.58%> (-0.04%)	⬇️

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