Destroy the plugin classes similar to `ProcessElfCore`, another process
plugin derived from `PostMortemProcess` class. After clearing thread
list, invoke `Finalize()` to cleanup resources properly. `Finalize()`
will call `DoDestroy()` which releases `m_kvm` via `kvm_close()`.
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Signed-off-by: Minsoo Choo <minsoochoo0122@proton.me>
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