Feature dsl schema shortcuts

[kasbaker]

This PR adds shortcuts for the remaining overloads for DSLSchema.__call__, including

• "__typename", "__schema", "__type" → DSLMetaField
• "..." → DSLInlineFragment
• "fragment" → DSLFragment (requires name to be a string)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (7fb869a) to head (27a4787).
⚠️ Report is 38 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##            master      #566    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           38        40     +2     
  Lines         2908      3235   +327     
==========================================
+ Hits          2908      3235   +327     

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[leszekhanusz]

Thanks, but please remove the "fragment" shortcut.

After sleeping on it I don't see the point.

Like I said it's not really a shortcut to use ds("fragment", "name") instead of DSLFragment("name") and the additional argument of __call__ is awkward.