Refactor internal building of schemas and improve error messaging

[austinvalle]

Closes #71

This PR introduces:

• Upgrading codegen-spec to v0.1.0: https://pkg.go.dev/github.com/hashicorp/terraform-plugin-codegen-spec@v0.1.0
• A refactoring of OAS schema building to setup future improvements to schema composition from #56
  • No functionality has been added, will now return more detailed error messaging if schema composition isn't supported

    Example error

    time=2023-10-13T11:57:08.836-04:00 level=WARN msg="skipping resource schema mapping" resource=insert_one oas_line_number=1418 err="found 2 allOf subschema(s), schema composition is currently not supported"

• Renaming PropertyError -> SchemaError as now line number information can be provided from more than just properties. Like when an array schema is completely empty!

Example error

time=2023-10-13T12:00:29.505-04:00 level=WARN msg="skipping mapping of create operation response body" resource=gists oas_path=fork_of.forks oas_line_number=83868 err="no 'type' array or supported allOf, oneOf, anyOf constraint - attribute cannot be created"

• Improvements to error messaging when a property name cannot be converted to a framework identifier, closing #71

  Past error

  time=2023-10-13T12:08:10.919-04:00 level=WARN msg="generated provider code spec failed validation" validation_msg="resources.0.schema.attributes.10.singlenested.attributes.1.name: Does not match pattern '^[a-z][a-z0-9_]*$'"

New error

time=2023-10-13T12:08:30.658-04:00 level=WARN msg="skipping mapping of create operation response body" resource=orgs oas_path=reactions.+1 oas_line_number=82619 err="'+1' cannot be converted to a valid Terraform identifier"

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