When converting concrete type pointers to interfaces with private methods
across packages, the interface metadata's PkgPath was incorrectly set to
the current compilation package instead of the interface definition package.
This caused the runtime to only fill exported methods in the itab, leaving
private method slots as NULL (0x0), which led to segmentation faults when
calling these private methods.
The fix extracts the package path from the interface's private methods
(if any) instead of using the current package path. This ensures the
runtime receives the correct package path for the visibility check.
Fixes#1370
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Co-authored-by: luoliwoshang <luoliwoshang@users.noreply.github.com>
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