Feature: Add option to run Lua scripts with EVAL_RO command instead of EVAL

[nantiferov]

Describe the problem

I noticed that redis_exporter executes provided Lua scripts with EVAL command. I'm not sure about all use cases of this feature, but at least in our case it's used to provide some stats from redis as metrics, which doesn't run anything changing data.

So I think it might be worth to add option to use EVAL_RO instead, which is read-only variant of the EVAL

If it will be disabled by default, it won't break anything, at the same time improving security as nothing bad will happen if Lua script will be compromised with destructive commands. Wdyt?

Running the exporter

redis_exporter -script test.lua

Additional context

NA

[oliver006]

I think that makes sense and is a good improvement re: security.