[BB-5107] feat: add GitLab CI runner terraform

Description

This PR adds GitLab runners set up by Terraform, using the npalm/gitlab-runner/aws module to resolve #3 (closed).

Related PRs

• https://gitlab.com/opencraft/dev/grove-development/-/merge_requests/62

Test instructions

1. Check the code diff
2. Check the attached terraform output (see below)
3. Check the OpenCraft Tools : Resources : Grove GitLab CI Runner record in vault
4. Run export GROVE_ENVIRONMENT="development"
5. Run terraform plan (the plan is NOT applied yet)

Notes

The instance resources may need to be set to higher instance types, but first, let's check if we are good with lower resources or not. Also, no IDLE instances were defined, hence the tool is not in production yet, so it would be waste of money. Later on, we could increase the value of runners_idle_count to increase the number of IDLE runners.

Resources

terraform-plan.out