[Relax][Frontend][NN] Fix SourceModule include resolution for installed wheels (#19822)

`SourceModule.get_includes()` hardcoded
`tvm_home()/3rdparty/tvm-ffi/...` paths that only exist in a source
checkout. In a wheel the tvm-ffi/DLPack headers ship in the separate
`tvm_ffi` package, so the existence assert failed and `nn.SourceModule`
could not compile extern sources.

This pr resolves includes via libinfo (`libinfo.find_include_path()`,
`tvm_ffi.libinfo.find_include_path()`, `find_dlpack_include_path()`),
matching `runtime/module.py` and `rpc/minrpc.py`.

Author: tlopex

python/tvm/relax/frontend/nn/extern.py

@@ -24,7 +24,9 @@
 from collections.abc import Callable
 from pathlib import Path
 
-from tvm import tirx
+import tvm_ffi
+
+from tvm import libinfo, tirx
 from tvm.runtime import Module, load_static_library
 from tvm.support import cc as _cc
 
@@ -306,15 +308,16 @@ def get_includes(tvm_pkg: list[str] | None = None) -> list[Path]:
         includes : List[pathlib.Path]
             The list of include paths.
         """
-        tvm_home = SourceModule.tvm_home()
         results = [
-            tvm_home / "include",
-            tvm_home / "3rdparty/tvm-ffi/include",
-            tvm_home / "3rdparty/tvm-ffi/3rdparty/dlpack/include",
+            Path(libinfo.find_include_path()),
+            Path(tvm_ffi.libinfo.find_include_path()),
+            Path(tvm_ffi.libinfo.find_dlpack_include_path()),
         ]
         if tvm_pkg:
+            tvm_home = SourceModule.tvm_home()
             for relative in tvm_pkg:
                 results.append(tvm_home / "3rdparty" / relative)
+        results = list(dict.fromkeys(results))
         for path in results:
             assert path.exists(), f"Not found: {path!s}"
             assert path.is_dir(), f"Not a directory: {path!s}"