[NPU] Refactor Plugin::import model in order to allow integrating the upcoming blob format in an OOP friendly manner

[razvanapetroaie]

Details:

intel_npu::Plugin::import_model (+ parse) have multiple duties, including:

• the extraction of the compiler main schedule
• the extraction of the compiler init schedules (weights-separation)
• ELF blob decryption
• reconstruction of the original model for its weights (weights-separation)
• Graph construction
• dummy ov::Model construction

Some of these operations depend on the format of the blob that is being used (raw compiler blob, compiler blob + metadata, the upcoming format). This PR aims to facilitate the integration of the upcoming format by refactoring the import_model to use the following class design:
TODO

Note that BlobFormatV2Handler and the BlobWriter related attributes/methods are not present in the current PR. These are intended to be added along with the upcoming blob format.

Tickets:

• CVS-190261

AI Assistance:

• AI assistance used: no