feat core: add tooltip params hideZeros

[vasily-sviridov]

What does this do?

Added a parameter for hideZeros tooltips, which can be used to hide null values in tooltips.

[casibbald]

@vasily-sviridov Please kindly show screen shots of before and after.

[vasily-sviridov]

With hideZeros=False:

With hideZeros=True:

hideZeros hides zero values from tooltips in Grafana panels, which is especially useful when there are many series, helping reduce visual noise and improve readability.

[vasily-sviridov]

@casibbald CI checks timed out. Can we restart them, please?

[vasily-sviridov]

@casibbald gentle ping