Async dashboard loading

[kron4eg]

What this PR does / why we need it:
This PR adds async loading of the data to the dashboard using HTXM, greatly speeding up the whole UI interactivity.

What type of PR is this?
/kind feature

Special notes for your reviewer:

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

Async dashboard loading

Documentation:

NONE

[kubermatic-bot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[kubermatic-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[kron4eg]

/cc @stroebitzer