CLOUDP-347875: Move GCI to go tool instead of Devbox

[roothorp]

Summary

GCI was causing issues with Devbox updates, so we can instead install it as a go tool and remove it from Devbox to circumvent the issue.

This does mean that we must invoke gci with go tool - the only place I found we use gci was in the fmt make target, which I have updated.

Proof of Work

Checklist

• Have you linked a jira ticket and/or is the ticket in the title?
• Have you checked whether your jira ticket required DOCSP changes?
• Have you checked for release_note changes?
• Have you signed our CLA?

Reminder (Please remove this when merging)

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  • --> no prefix is considered a question