SME-228/LIB-70: Support OpenTofu, replace tfenv/tgswitch with Mise

[arsci]

Description

Closes #53

• Add support for OpenTofu
  • Adds use of INPUT_TOFU_VERSION. If this environment variable is supplied (instead of INPUT_TF_VERSION) Mise will install OpenTofu and set TERRAGRUNT_TFPATH=tofu when invoking Terragrunt to use tofu instead of terraform.
• Replaced tfenv and tgswitch with mise due to unpatched vulnerabilities
• Refactor tests
  • Add tests for OpenTofu support
  • Refactor test structures
  • Add precommit step (terraform-fmt/goimports)
  • Add test logging/test artifact upload to CircleCI

Release Notes

Added support for OpenTofu, added Mise, removed tfenv/tgswitch

[gruntwork-ci]

Upgrade test results for build 154