[Monitoring UI] Re-add Chart tooltip.

[elasticmachine]

Original comment by @tsullivan:

Having the chart tooltip in the UI made it really nice to see the value of a point I'm hovering on. My eyes find it hard to move quickly to the horizontal legend at the bottom to see this number.

We just need to make sure that if we bring back the deleted code, at the same time we fix any bugs calculating it's left/right orientation.

[elasticmachine]

Original comment by @skearns64:

Thanks for opening the issue! This is a lower priority than the open bugs we discussed today, but is good to capture.

[elasticmachine]

Original comment by @tsullivan:

The current Monitoring chart was originally copied from Thor (now called Timeseries Visual Builder) in 5.2. The chart tooltip was pulled out because it had orientation issues that made the text get cut off.

There is currently a similar issue in TSVB: #12866

[elasticmachine]

Original comment by @tsullivan:

PR where tooltip was removed: LINK REDACTED

[elasticmachine]

Original comment by @tsullivan:

There are functions added in LINK REDACTED that will make this nice and easy

[elasticmachine]

Original comment by @tsullivan:

this would be nice to have, but I'm tempted to close this in favor of LINK REDACTED

[cachedout]

Since this is already a part of an the effort to replace charts, that's being tracked here (among other places): elastic/elastic-charts#65 I am closing this as a duplicate.