Expose equal and in operators as part of the schema response

[soupi]

What

rc14 requires we expose the equal and in operators as part of the schema response.
To do that, we have to specify them as part of the metadata.

How

• We add a new attribute to operators - OperatorKind, which will say whether an operator is equal, in or custom, similar to ComparisonOperatorDefinition.
• In the introspection, we map the _eq operator to the kind Equal, and other operators to Custom.
• In the introspection, we check if a scalar type has the equal operator, and add it the in operator as well if yes.
• We change the filtering code so that it checks the operator kind of an operator to distinguish in from the rest, instead of looking at the name.
• We regenerate the ndc-metadata and fix the tests

We also:

• Moved version3.* into the version3/ dir
• Removed the old v1 and v2 config tests.