Provide more clear error message if the user-provided cors_origin is malformed

In 1.5.2 we added the possibility for the operators to specify the CORS origin via config. The issue is that there is no proper error handling in warp, instead it simply panics when the provided string can't pass validation, leaving user with the "cryptic" error message, like "node panicked: missing scheme". Details and proposed solutions are described in the comment
[here](https://github.com/casper-network/casper-node/pull/4105#issuecomment-1632109250)