Added WithErrorCheck option to redis

[lsgndln]

What does this PR do?

This PR adds a WithErrorCheck to the redis packages. I originally created an issue here that was accepted.

Motivation

The goal of this option is to have a way to define which error should be marked as a datadog error.

For example, a context.Canceled error could be ignored in datadog.

redistrace.WithErrorCheck(func(err error) bool {
    return err != nil && !errors.Is(err, context.Canceled)
})

Describe how to test/QA your changes

I added tests in the different packages, they can be checked to see how to test the changes.

The custom error check function can be added to the client as an option :

errCheckFn := func(err error) bool {
    return err != nil && !errors.Is(err, context.Canceled)
}
		
client := NewClient(opts, WithServiceName("my-redis"), WithErrorCheck(errCheckFn))

Reviewer's Checklist

• Changed code has unit tests for its functionality.
• If this interacts with the agent in a new way, a system test has been added.