Add an option which only root user can execute Windows binary in WSL

**Is your feature request related to a problem? Please describe.**
I want that only root user is able to execute Windows binary in WSL.

**Describe the solution you'd like**
There is an option like `rootOnly` to enable this feature in `wsl.conf`. For example,
```service
[interop]
rootOnly = true
```
And when WSL non-root user execute Windows binary will produce proper error message.
```sh
firejox@DESKTOP-2BCQGK7:~$ xxx.exe
xxx.exe permission denied
```

**Describe alternatives you've considered**
Currently, I can use `chmod o= /run/WSL` to forbid non-root user execute Windows binary. However, it produces ugly error message.
```sh
firejox@DESKTOP-2BCQGK7:~$ choice.exe
<3>WSL (841) ERROR: UtilConnectUnix:513: connect failed 13
firejox@DESKTOP-2BCQGK7:~$
```

Start by reading the [interop] settings in wsl.conf and tracing the current Windows-binary execution path, including the /run/WSL alternative mentioned in the issue. Define how rootOnly should be parsed and enforced, then verify that non-root execution produces a clear permission-denied result while root execution remains supported.

Written by the indexing model from the issue text.