EPP: Replace reservation extenion with rfc8495

[vohmar]

We currently use .ee specific extnsion for reserved and auctioned domains registrations

https://github.com/internetee/registry/blob/master/lib/schemas/eis-1.0.xsd

There is a proposed standard out for the same purpose: https://tools.ietf.org/html/rfc8495

Consider switching for standardised approach

[artur-intech]

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