[API-Processor] Support removeOasExtensions build task

[iugaidiana]

1. The builder shall be able to removeOasExtensions build task, which shall remove OpenAPI extensions and their values from one or multiple OpenAPI specifications.
   • Builder shall be able to remove OpenAPI extensions only for the following document types: openapi-3-1, openapi-3-0, openapi-2-0
2. For the existing build tasks - reducedSourceSpecifications and mergedSpecification, the builder shall support new flag removeOasExtensions (boolean). If removeOasExtensions = true, the system shall remove OAS extensions and their values from the resulted OAS specifications (specs after reducing source specs or after merge specs).
3. The builder shall remove all OpenAPI extensions excluding the list of allowed of OAS extensions.
   • List of allowed list of OAS extensions will be provided in build config.
   • If list of allowed of OAS extensions is empty, then all OAS extensions shall be removed.
4. If found OAS extension is object, then builder shall remove entire object with all child extensions.
5. If found OAS extension is array, then builder shall remove entire array with all values.
6. The builder shall search for OAS extensions to delete only on the first level of OAS extensions, i.e. child extension cannot be removed separately from its parent extension.
7. The builder shall search for OAS extensions only in places allowed by OpenAPI specifications. If some OAS extension is specified in the place which is not allowed by OAS specification, then the builder shall skip (i.e. not delete) such extension.
   • List of possible locations of OAS extensions can be found at https://github.com/OAI/OpenAPI-Specification/blob/main/_archive_/schemas/v3.0/schema.yaml

[CountRedClaw]

qubership-apihub-api-unifier implementation plan:

1. Add optional phase for OAS extensions removal (disabled by default). The phase should be executed before the hash phase (because validation should trim all the places where extensions are not allowed). But validation phase should not be used simultaneously with the OAS extensions removal phase.
2. Phase activation is an option with predicate to the root extension. It should have the extension key as an input and a boolean value as an output. If the predicate returns true - the extension should be removed, and it should do nothing otherwise.
3. Create a hook that uses a crawler with clone. The hook should also remove the origins if the extension is being removed.
4. The phase should have no effect in case if the spec type is GQL.

qubership-apihub-api-processor implementation plan:

This part is descoped in favor of Netcracker/qubership-apihub-api-processor#10

1. Add a new build task.
2. Add the following strategies:
   GQL should have no effect.
   OAS should execute the normalize function with only OAS extensions removal phase activated (all other phases should be deactivated). The strategy should receive a list of allowed extensions and should define a predicate based on this list.