Add lightstep tracer plugin

[robherley]

Description

Adds a tracer plugin for lightstep that points to a collector.

Related Issue(s)

n/a

Checklist

• "Backport to:" labels have been added if this change should be back-ported
• Tests were added or are not required
• Documentation was added or is not required

Deployment Notes

[robherley]

@arthurschreiber the e2e CI errors were because I originally modeled this after the head of the main vitess branch that uses viper (vitess.io/vitess/go/viperutil) instead of pflag (vitess.io/vitess/go/flagutil)

• [RFC] Standardized viper framework for vitess configuration parameters vitessio/vitess#11456

not sure when we'll get up to that in this fork 🤷
also not sure why the upgrade/downgrade tests are having issues with the go modules

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[github-actions]

This PR was closed because it has been stale for 7 days with no activity.