Adds writers for Fields, OrderedElements, and logic constraints

[popematt]

Issue #, if available:

None

Description of changes:

• Adds writers for more constraints.
• Adds convenience constructors for constraints that accept a list of type arguments
• Adds factory methods for constructing a VariablyOccuringTypeArgument from a TypeArgument
• Moves writeTypeArguments from the TypeWriter interface to be an extension function instead.

Related PRs in ion-schema, ion-schema-tests, ion-schema-schemas:

None

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Attention: 40 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
...n/ionschema/model/VariablyOccurringTypeArgument.kt	88.88% <83.33%> (ø)
...com/amazon/ionschema/writer/internal/TypeWriter.kt	0.00% <0.00%> (ø)
...schema/writer/internal/constraints/FieldsWriter.kt	72.72% <72.72%> (ø)
...in/kotlin/com/amazon/ionschema/model/Constraint.kt	70.90% <50.00%> (ø)
...iter/internal/constraints/OrderedElementsWriter.kt	0.00% <0.00%> (ø)
...ter/internal/constraints/LogicConstraintsWriter.kt	0.00% <0.00%> (ø)

... and 132 files with indirect coverage changes

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[desaikd]

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