`net.box.self.call` majorly affects the performance of `vshard`

[Serpentian]

net.box.self.call is slow: tarantool/tarantool#11624 and will probably be dropped in the Tarantool 4.0. Even if it will be fixed instead, we need to support Tarantool 2.11, and these new fixes cannot be backported there. We need to introduce our own implementation of the local call, which should be much more efficient, that encoding and decoding msgpacks, which is done in net.box