optimize vr runtime detection

[sofoxe1]

idk c# and didn't test since i don't use this feature but similar implementation works here: https://codeberg.org/sofoxe1/xr_overlay/src/commit/614c687827913e9585a432d62b9e0eae7b976e99/core/src/xr/mod.rs#L234
i will have to look at how steamvr works to avoid process scanning when checking for it

[Natsumi-sama]

IsSteamVRRunning is only used on Linux, is Process.GetProcessesByName() really that bad on Linux? I feel like this PR would introduce bugs more than anything else. I'd like to get some input from other Linux users if they can test how Process.GetProcessesByName() performs.

[sofoxe1]

the only issue it causes is the cpu usage number in the process monitor, as for bugs depends what exactly vrcx should detect as running for example for application to be able to start under wivrn both config and pipe needs to be present but it needs the config only when loading openxr and wivrn could also randomly crash without cleaning those files