[EASI-3172] Upgrade go from 1.18 to 1.21

[ClayBenson94]

EASI-3172

Changes and Description

• EASI-3176: Upgrade Go version to 121 mint-app#682
• Modified references to go 1.18 to go 1.21
• Updated linters to use new versions that support go 1.21
• Updated docker volume mounts to only volume mount items that we need (comments explain at a high level why this is necessary, but tl;dr - mounting the .git directory in docker causes some issues with Go 1.21)

How to test this change

• Start up the server locally with scripts/dev up, ensuring the app can build
• Use scripts/dev db:seed to seed the DB
• Play around with the app - give a smoke test to make sure things like submitting new requests works, System Profile works, login with Okta works, etc.
• Ensure E2E tests pass

PR Author Review Checklist

• Met the ticket's acceptance criteria, or will meet them in a subsequent PR.
• Added or updated tests for backend resolvers or other functions as needed.
• Added or updated client tests for new components, parent components, functions, or e2e tests as necessary.
• Tested user-facing changes with voice-over and the rotor menu

PR Reviewer Guidelines

• It's best to pull the branch locally and test it, rather than just looking at the code online!
• Check that all code is adequately covered by tests - if it isn't feel free to suggest the addition of tests.
• Always make comments, even if it's minor, or if you don't understand why something was done.

[DylanSpOddball]

Looks good overall; I have two small comments, but they're not significant enough to hold up this PR. We might also want to reference installing our current version of Go in docs/dev_environment_setup.md; right now it just says to install the latest version of Go. Up to you, though.

Once this gets merged, it'd be a good idea to let the team know to upgrade their locally installed versions of Go.

[DylanSpOddball]

Looks good with updates to docs.

Side note - it looks like the issues with that gosec rule might have been fixed by securego/gosec#1017, but we can look into that later.