Minor improvements to API server dashboard

[lnovara]

This PR improves the API server dashboard by adding minimums to Y-axis of every plot and moving the singlestat panel on its own row to give the dashboard a more homogeneous structure.

[brancz]

cc @povilasv

[lnovara]

@brancz @povilasv There are also other minor issues like these in the other dashboards, do you want me to address them in separate PRs or we can pack everything into this one?

Thank you.

[brancz]

I'd say let's do small separate PRs. Also it would help immensely if you could attach a screenshot of before after, if it's not too much trouble :)

[lnovara]

Thank you @brancz, I will open other PRs.

Meanwhile, here you have the before and after screenshots of the dashboard:

Before:

After:

[povilasv]

I'm not sure whether it makes sense to make up have a separate row, as those dashboards are quite a long already.

Other changes LGTM

[brancz]

Agreed regarding the up panel.

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