Consider Handling of Terraform-specific Behaviour Properties

### Use Cases or Problem Statement

Automated generation of provider schema Go code for predefined Plan Modifiers would simplify code generation.

Currently, in order to have a predefined Plan Modifier appear in the generated schema, the spec that is fed to the generator needs to explicitly define the Plan Modifier as follows:

```json
"plan_modifiers": [
{
"custom": {
"imports": [
{
"path": "github.com/hashicorp/terraform-plugin-framework/resource/schema/stringplanmodifier"
}
],
"schema_definition": "stringplanmodifier.UseStateForUnknown()"
}
}
]
```

If [Consider Adding Terraform-specific Behaviour Properties](https://github.com/hashicorp/terraform-plugin-codegen-spec/issues/85) is implemented in codegen-spec, then modifications to codegen-framework will be required in order to process these new fields in the spec.

### Proposal

Track [Consider Adding Terraform-specific Behaviour Properties](https://github.com/hashicorp/terraform-plugin-codegen-spec/issues/85) is implemented in codegen-spec, and add relevant code to process new behaviour properties if/when they are added to codegen-spec.

### Additional Information

References:

- [Consider Adding Terraform-specific Behaviour Properties](https://github.com/hashicorp/terraform-plugin-codegen-spec/issues/85)
- [Remove Framework-specific Implementation Details from Plan Modifiers](https://github.com/hashicorp/terraform-plugin-codegen-spec/issues/83#top)
- [Removing framework-specific implementation details from plan modifiers](https://github.com/hashicorp/terraform-plugin-codegen-spec/pull/84#top)

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct