feat: adding `rpc_servers` parameter to `Llama` class (#1477)

* passthru rpc_servers params

wip

* enable llama rpc by default

* convert string to byte

* add rpc package

* Revert "enable llama rpc by default"

This reverts commit 832c6dd56c979514cec5df224bf2d2014dccd790.

* update readme

* Only set rpc_servers when provided

* Add rpc servers to server options

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Co-authored-by: Andrei Betlen <abetlen@gmail.com>