move runner and export it

[ceyonur]

Why this should be merged

Makes it possible for external programs to import the main runner function from subnet-evm like

in another repo's plugin/main.go:

// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.

package main

import (
	"github.com/ava-labs/subnet-evm/plugin/runner"

	_ "github.com/ava-labs/precompilevm/helloworld"
)

func main() {
	runner.Run()
}

How this works

moves main function to a separate exported package

How this was tested

Locally tested

How is this documented

Will add a new repo for example and document it.

[darioush]

should we add a string argument so the external repo can add some text to the PrintVersion message?

[aaronbuchwald]

Agreed it would be nice to allow an external repo to optionally specify some additional output to be included in PrintVersion().

[ceyonur]

added

[anusha-ctrl]

lgtm

[aaronbuchwald]

Adding the DO NOT MERGE label as @ceyonur and I talked offline that we want to spend a little more time thinking about the best way to do this before putting out an example that we would expect the community to start using.