[Integration][Gitlab-v2] Support resolving file:// references in file content

[shariff-6]

Description

What
This pull request introduces support for resolving file:// references in file content , enabling dynamic fetching of referenced file content during parsing.

Why
Resolving file:// references allows for more flexible configuration files, where content can be modularized across multiple files. This improves maintainability and supports complex workflows in GitLab projects, addressing user needs for dynamic content inclusion.

How

• Added resolve_file_references function in gitlab/helpers/utils.py to recursively process file:// references and fetch their content.
• Updated GitLabClient._process_file in gitlab/clients/gitlab_client.py to integrate reference resolution after parsing file content.
• Introduced FileClientProtocol in utils.py for type-safe client interactions.
• Added a test case in tests/clients/test_base_client.py to verify the resolution of file:// references in parsed YAML content.

Type of change

Please leave one option from the following and delete the rest:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• New Integration (non-breaking change which adds a new integration)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Non-breaking change (fix of existing functionality that will not change current behavior)
• Documentation (added/updated documentation)

All tests should be run against the port production environment(using a testing org).

Core testing checklist

• Integration able to create all default resources from scratch
• Resync finishes successfully
• Resync able to create entities
• Resync able to update entities
• Resync able to detect and delete entities
• Scheduled resync able to abort existing resync and start a new one
• Tested with at least 2 integrations from scratch
• Tested with Kafka and Polling event listeners
• Tested deletion of entities that don't pass the selector

Integration testing checklist

• Integration able to create all default resources from scratch
• Resync able to create entities
• Resync able to update entities
• Resync able to detect and delete entities
• Resync finishes successfully
• If new resource kind is added or updated in the integration, add example raw data, mapping and expected result to the examples folder in the integration directory.
• If resource kind is updated, run the integration with the example data and check if the expected result is achieved
• If new resource kind is added or updated, validate that live-events for that resource are working as expected
• Docs PR link here

Preflight checklist

• Handled rate limiting
• Handled pagination
• Implemented the code in async
• Support Multi account

Screenshots

Include screenshots from your environment showing how the resources of the integration will look.

API Documentation

Provide links to the API documentation used for this integration.

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