[installer] move workspaceImage out of experimental config

[nandajavarma]

Description

This PR moves out options to specify the default workspace image and the allowList of private image registries out of the experimental section.
The workspace image and the allow list for the registry can be specified as follows:

workspace:
  workspaceImage: 691173103445.dkr.ecr.eu-west-1.amazonaws.com/691173103445.dkr.ecr.eu-west-1.amazonaws.com/busybox:new
containerRegistry:
  privateBaseImageAllowList:
    - 691173103445.dkr.ecr.eu-west-1.amazonaws.com

Related Issue(s)

Fixes #10791
Fixes #11408

How to test

• Open this PR in a gitpod workspace with access to the core-dev cluster.
• Download the replicated license corresponding to this channel.
• mkdir -p installer/licenses/nvn/
• cp path/to/replicatedlicense installer/licenses/nvn/fix-11408.yaml`

werft run github -s installer/licenses/nvn/fix-11408.yaml -j .werft/eks-installer-tests.yaml -a preview=true -a channel=nvn/fix-11408 -a skipTests=true -a deps=external

• You will find the kubeconfig content under the get-results tab of the task on werft.
• Connect the cluster, open KOTS CLI and provide the above config as config_patch.yaml

Release Notes

NONE

Documentation

Werft options:

• /werft with-preview

[nandajavarma]

/werft run no-preview publish-to-kots

👍 started the job as gitpod-build-nvn-fix-11408.17
(with .werft/ from main)

[andrew-farries]

Changes look fine - just a question about deprecation vs removal.

[mrsimonemms]

LGTM

Have you created a deprecation task and assigned to a future milestone? I'd suggest putting one in the December milestone similar to #11124. Also, link it to this PR so it's easily findable when we forget everything in future

[1cor13]

Do you have an example gitpod.yml on how I can use my private image hosted on dockerhub.