Override hubble-ui images if overwriteRegistry is set

[embik]

What this PR does / why we need it:

As reported, the hubble-ui frontend and backend images are not correctly overridden if overwriteRegistry is set. Turns out, the valuesFrontend and valuesBackend variables prepared for it where never added to the main values map.

To make this PR backport-compatible for 2.24, I am also not setting the podSecurityContext that would have been part of cloning the common values into valuesFrontend and valuesBackend. The value doesn't exist anyway.

In addition, I have moved the construction of the final values map from the sub-maps to the end of the function. I found it deeply confusing that the maps are wired up into values first and then set.

Which issue(s) this PR fixes:

Fixes #13136

What type of PR is this?
/kind bug

Special notes for your reviewer:

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

Fix missing image registry override for hubble-ui components if Cilium is deployed as System Application

Documentation:

NONE

[embik]

/cherry-pick release/v2.24

[kubermatic-bot]

@embik: once the present PR merges, I will cherry-pick it on top of release/v2.24 in a new PR and assign it to you.

In response to this:

/cherry-pick release/v2.24

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[embik]

/cc @cnvergence

[embik]

/milestone KKP 2.25

[cnvergence]

lgtm

[kubermatic-bot]

LGTM label has been added.

Git tree hash: ef8a69ccd53063be9b424ae7703b6da8a46dab28

[cnvergence]

/approve

[kubermatic-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cnvergence

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[kubermatic-bot]

@embik: new pull request created: #13140

In response to this:

/cherry-pick release/v2.24

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.