Add support for `string-able` multi-types, allOf overrides, and improve error messaging

[austinvalle]

Closes: #57 Ref: #56

This PR introduces:

• Support for string-able types, which are a multi-type or oneOf/anyOf composition of exactly two, with one type being a string, and the other being a primitive (int, number, bool, etc.)
  • Similar to currently supported null-able type
• Support for using the allOf constraint with exactly one entry. Examples of this are in the kubernetes testdata, which use allOf to override the description of the common "base" schemas.
  • I also added the overriding of descriptions into the logic 👍🏻

Examples of error logging

Prior to adding the allOf support:

time=2023-09-29T13:08:23.155-04:00 level=WARN msg="skipping resource schema mapping" resource=deployment_v1 err="property does not have a 'type' or supported allOf, oneOf, anyOf constraint - attribute cannot be created" oas_property=metadata oas_line_number=377

Prior to adding the string-able support:

time=2023-09-29T13:08:55.626-04:00 level=WARN msg="skipping resource schema mapping" resource=deployment_v1 err="[integer, string] - unsupported multi-type, attribute cannot be created" oas_property=spec.strategy.rollingUpdate.maxSurge oas_line_number=879

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