[cleanup] Remove deprecated code marked for 1.2.0 release

[Viscous106]

Summary
This PR removes multiple instances of deprecated code that were marked for removal in release 1.2.0 (or earlier). This cleans up technical debt in the config, tasks, and controller views.

Changes

• Config (config.py): Removed the deprecated get_cached_args compatibility wrapper.
• Tasks (tasks.py): Removed the deprecated invalidate_device_checksum_view_cache task.
• Views (views.py): Removed legacy support for status="running" in DeviceReportStatusView. The modern status="applied" logic is preserved.
• Tests (test_controller.py): Removed test_device_report_status_running which tested the deprecated "running" status.

Verification

• Ran python tests/manage.py test openwisp_controller.config
• Result: Passed. Verified that test_device_report_status_applied still passes and the controller handles status updates correctly.

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[nemesifier]

@Viscous106 why did you close this?

[Viscous106]

Hi @nemesifier, apologies for closing this so out of the blue. I was hitting persistent CI failures despite the tests passing locally, so I stepped back to debug my environment.

I have since read Discussion #1181 and fixed my setup. I am ready to resolve the remaining checks now, so I will reopen this.

[Viscous106]

Hi @nemesifier,

I have fixed the linting and environment issues we discussed. However, to ensure a clean commit history and avoid the confusion caused by the previous branch reset, I have opened a fresh PR with the finalized fixes.

Superseded by #1190.

Thanks!