RequestServer: Transfer ownership of Protocols to all_protocols map

[ADKaster]

It's no change in application behavior to have these objects owned by the function-scope static map in Protocol.cpp, while allowing us to remove some ugly FIXMEs from time immemorial.

I thought about converting this to some kind of clever RequestServer::register_protocols({"gemini"sv, "http"sv, "https"sv}) API or something, but this seems simpler :)