Baremetal image builds must allow for configuring builder VM resources

I have already searched through all Issues and Pull Requests, and did not find a similar request.

**What would you like to be added**:

We consistently are unable to provision the necessary packages inside the baremetal image build, as the default upstream capi template is 6144MB. Normally, image-builder allows for packer variable overrides but this is not possible with the custom eks-anywhere provided image-builder tooling.

Either expose the variables to be configured for `cpus`, `memory`, and `disk_size` or at least allow for a packer variables file to be passed into the build command.

**Why is this needed**:

Without this capability, we may need to implement a fully custom image building process, implement a re-packaging of the EKS-Anywhere created image, or run our full provisioning workflow during the Tinkerbell provisioning process. The last option is the most feasible, yet also the most prone to failure during cluster creation or updated.

Start by tracing the baremetal image build command and the custom EKS-Anywhere image-builder tooling that prevents Packer variable overrides. Determine where builder VM resources are fixed and review how the build consumes Packer variables. Done means the build can configure cpus, memory, and disk_size or accept a variables file, with package provisioning succeeding under the increased resources.

Written by the indexing model from the issue text.