Handle unsigned DLLs with onnx-hipddn-ep

[fhanuman]

Context: During the design discussion in the hipDNN workgroup meeting, several ideas were proposed for addressing the unsigned DLL issue in onnx-hipdnn-ep through a DLL separation approach. Using this issue to track the proposal and ideas.

[akholodnamdcom]

The proposal to this security problem is quite simple:
Do not put anything executable to disk (neither DLL nor BC).

Doing otherwise makes software, that uses our ep, vulnerable (potential privilege escalation CVE).

[akholodnamdcom]

This not okay to require winsdk/vs to be installed on client machine:

     lld-link: error: could not open 'msvcrt.lib': no such file or directory
     lld-link: error: could not open 'ucrt.lib': no such file or directory
     lld-link: error: could not open 'vcruntime.lib': no such file or directory
     lld-link: error: could not open 'oldnames.lib': no such file or directory
     lld-link: error: could not open 'libcpmt.lib': no such file or directory
     lld-link: error: could not open 'libcmt.lib': no such file or directory
     lld-link: error: could not open 'kernel32.lib': no such file or directory
     lld-link: error: could not open 'user32.lib': no such file or directory
     LLD-LINK failed with exit code: 1
     E20260501 09:22:07.891604 23636 MlirCompiler.cpp:122] Compilation failed: Failed to link DLL

Or Im missing something?