Types for objc_retain_xN / objc_release_xN in the libobjc type library should include their custom calling conventions

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Version and Platform (required):

• Binary Ninja Version: 5.3.9301-dev Ultimate, 855e811
• OS: macos
• OS Version: 26.3.1
• CPU Architecture: arm64

Bug Description:

>>> bv.import_library_object('_objc_release_x20')
<type: immutable:FunctionTypeClass 'void()'>
>>> bv.import_library_object('_objc_release_x20').calling_convention

Expected Behavior:
These functions should:

1. Have the correct signature: id _objc_release_x20(id).
2. Specify the custom calling convention (apple-arm64-objc-fast-arc-20) to make explicit that the argument is not passed via x0.

Additional Information:
Both the shared cache and Mach-O views have to work around this at present by recognizing imports of these functions and manually fixing up the signature and calling convention.