deps: remove go.mod files from submodules

[daniel-weisse]

Context

We want to get rid of our multiple go.mod files in submodules and use just a single go.mod file for our project.

Proposed change(s)

• Remove go.mod files

Additional info

• e2e CLI
• e2e Terraform

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[github-actions]

Coverage report

Package	Old	New	Trend
cli/internal/cmd	58.50%	58.50%	↔️
hack/gocoverage	59.20%	59.20%	↔️
internal/constellation/kubecmd	67.90%	67.90%	↔️
operators/constellation-node-operator	0.00%	[no test files]	🚨
operators/constellation-node-operator/api	0.00%	[no test files]	🚨
operators/constellation-node-operator/api/v1alpha1	0.00%	[no test files]	🚨
operators/constellation-node-operator/controllers	0.00%	30.80%	🆕
operators/constellation-node-operator/internal/cloud/api	0.00%	[no test files]	🚨
operators/constellation-node-operator/internal/cloud/aws/client	0.00%	78.40%	🆕
operators/constellation-node-operator/internal/cloud/azure/client	0.00%	88.90%	🆕
operators/constellation-node-operator/internal/cloud/fake/client	0.00%	[no test files]	🚨
operators/constellation-node-operator/internal/cloud/gcp/client	0.00%	80.80%	🆕
operators/constellation-node-operator/internal/constants	0.00%	[no test files]	🚨
operators/constellation-node-operator/internal/controlplane	0.00%	100.00%	🆕
operators/constellation-node-operator/internal/deploy	0.00%	76.60%	🆕
operators/constellation-node-operator/internal/etcd	0.00%	65.80%	🆕
operators/constellation-node-operator/internal/executor	0.00%	89.50%	🆕
operators/constellation-node-operator/internal/node	0.00%	100.00%	🆕
operators/constellation-node-operator/internal/patch	0.00%	100.00%	🆕
operators/constellation-node-operator/internal/poller	0.00%	91.40%	🆕
operators/constellation-node-operator/internal/upgrade	0.00%	[no test files]	🚨
operators/constellation-node-operator/sgreconciler	0.00%	34.90%	🆕
terraform-provider-constellation	[no test files]	[no test files]	🚧

[elchead]

can you link a test run for the provider and a normal CLI cluster?

[msanft]

Terraform E2E Test issue is unrelated to this PR, i think this should be good to merge.

[malt3]

Let's merge this to unblock pending dependency upgrades. I built everything locally for testing purposes and it looks very promising!