Fix support for ca-bundle

[ahmedwaleedmalik]

What this PR does / why we need it:
This PR fixes the ca-bundle flag/support in OSM. This flag is used to override the PKI certs for Kubernetes. Although in our other tools like machine-controller, KubeOne, the functionality is a bit different and this is used to override the CA certs for the host and in-code clients that communicate with external services.

To clear this ambiguity, we have to split it into kubernetes-ca-bundle and host-ca-bundle flags to make it coherent and self-explanatory. The flag ca-bundle has been deprecated and made no-op.

Which issue(s) this PR fixes:

Fixes #235

What type of PR is this?

/kind feature
/kind deprecation

Special notes for your reviewer:

Does this PR introduce a user-facing change? Then add your Release Note here:

* Introduce `kubernetes-ca-bundle` and `host-ca-bundle` to propgate custom CA certs to kubernetes worker node and the machine itself, respectively.
* The flag `ca-bundle` has been deprecated and is now no-op. Please use `kubernetes-ca-bundle` or `host-ca-bundle` instead.

Documentation:

NONE

[kron4eg]

Found few forgotten names.

[kron4eg]

/approve

[kubermatic-bot]

LGTM label has been added.

Git tree hash: f5109822da30207a9842a8e00313408cdb92fad5

[kubermatic-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kron4eg

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[kron4eg]

/cherrypick release/v1.5

[kubermatic-bot]

@kron4eg: #399 failed to apply on top of branch "release/v1.5":

Applying: Fix support for ca-bundle
Using index info to reconstruct a base tree...
M	cmd/osm-controller/main.go
M	deploy/osps/default/osp-ubuntu.yaml
M	go.mod
M	go.sum
M	pkg/controllers/osc/osc_controller.go
M	pkg/controllers/osc/resources/operating_system_config.go
Falling back to patching base and 3-way merge...
Auto-merging pkg/controllers/osc/resources/operating_system_config.go
Auto-merging pkg/controllers/osc/osc_controller.go
Auto-merging go.sum
CONFLICT (content): Merge conflict in go.sum
Auto-merging go.mod
CONFLICT (content): Merge conflict in go.mod
Auto-merging deploy/osps/default/osp-ubuntu.yaml
Auto-merging cmd/osm-controller/main.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Fix support for ca-bundle
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherrypick release/v1.5

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