Upgrade `github.com/pb33f/libopenapi` to `v0.14.4`

[austinvalle]

Supersedes #109, #113

This PR contains a version bump from github.com/pb33f/libopenapi v0.13.22 -> v0.14.4, along with all the fixes for breaking changes to the code structure. The original release notes can be found in the linked dependabot PR (#109) but I will summarize the effects on tfplugingen-openapi here.

Fixes from downstream

• I can't find a relevant GH issue from downstream, but the only change I see to our acceptance tests are that int32 default values are now properly being detected, where before they must have been not populated properly? I created a changelog for it, but the related OpenAPI spec's seem to match the behavior we have now 👍🏻 . All 3 of the properties showing changes in the kubernetes test look the same:

Changes from downstream

• The biggest change is the libopenapi data model can be traversed in the exact order as defined in the OpenAPI spec, this manifests itself in a switch from using the Go built-in map, to a new orderedmap type. The construction of this type in tests has changed as well as how you iterate over it.
  • Iterating over the orderedmap now requires a context.Context, which I have replaced with a context.TODO for now.
• The (Parameter).Required field changed from bool to *bool
• (Schema).Default and (Schema).Enum now use *yaml.Node instead of any . Type assertions have been replaced with YAML unmarshaling/decoding.

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