NativeLibraryTests: Platform restriction on some tests (dotnet/coreclr#22732)

NativeLibraryTests: Platform restriction on some tests (dotnet/coreclr#22732)

NativeLibraryTests: Platform restriction on some tests

This change adds platform restrictions on two API tests:
* Change the System32 dll loading test from `msi.dll` to `uri.dll`
* Restrict the System32 dll loading test to platforms where `uri.dll` actually exists in the System32 directory.
* Disable double-free tests on Linux, because the OS call doesn't reliably fail.

Use the public version of CoreLib, since the NativeLibrary APIs are
now available.

Fixes dotnet/coreclr#22726

Commit migrated from https://github.com/dotnet/coreclr/commit/c395a8a8e7a987000455d65efac371973d96a3c8