Auto TrustDomain

[kfox1111]

https://github.com/spiffe/spire-controller-manager/blob/main/cmd/main.go#L229 requires the trust domain to be set. But its pretty much the only setting that must be set in a default config. It should be possible to get the trust domain from the spire-server and then auto configuration should be possible, making for a better out of the box configuration?