Make processor backward compatible

It would be super useful if we could turn our `Processor` to be backward compatible wrt package version. Tooling that heavily depends on the `Processor` can only support the latest package version, but it would be nice if end user can use e.g. debugger on some older binaries they have.

Please let me know your thoughts.

cc @huitseeker @bitwalker @bobbinth

Look at the Processor struct and its version handling in the codebase. Understand how package versions are currently managed and where backward compatibility would need to be added. Check existing tests for the Processor to see how version changes are tested. The goal is to allow tooling like debuggers to work with older binaries.

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