Fix issues with build stage. Set correct project name for db-benchmarking
The build stage failed to run because Packer couldn't find the variables.pkr.hcl file with the variables definitions.
We have modified the packer build command to use the folder instead of the build file so it automatically loads this file. We have also corrected the name of the gitlab-db-benchmarking google project.
Related Issue: https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/14487