Fixes#1436
This is a temporary implementation of the `feature` RPC that will always
return `noPermission` iff `vetoed` is set.
If `vetoed` isn't specified, Clio will always forward the request to
`rippled` instead.
In the future, #1131 will implement a Clio-native `feature` RPC. This
requires specific support from `libxrpl` side and that is not going to
be available till at least 2.2.1, hence the temporary forwarding.
It would be great to review the error message and code so that we pick
the right one from the start.
Co-authored-by: Sergey Kuznetsov <skuznetsov@ripple.com>
