MINIFICPP-2805 Move reinterpret casts into functions in minifi-c.cpp

[martinzink]

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[Copilot]

Pull request overview

This PR refactors the MiNiFi C API bridge layer by centralizing C↔C++ reinterpret-casts and string-view conversions into a shared utility header, reducing repetition and making the API boundary code easier to audit and maintain.

Changes:

• Introduces utils/minifi-api-utils.h with shared helpers for string conversion and generic toC / toCpp casts between opaque C handles and C++ types.
• Updates libminifi/src/minifi-api.cpp to use the new helpers instead of ad-hoc reinterpret_cast and local conversion functions.
• Updates CProcessor and CControllerService wrappers to use the shared helpers for logger and context/session casting.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
libminifi/src/minifi-api.cpp	Replaces local string helpers and repeated reinterpret_cast usage with centralized utility helpers.
libminifi/include/utils/minifi-api-utils.h	Adds shared conversion utilities and type mapping for opaque C API handles.
libminifi/include/utils/CProcessor.h	Switches C API callback argument casting and metadata packing to use the new helpers.
libminifi/include/utils/CControllerService.h	Switches C API callback argument casting and metadata packing to use the new helpers.

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