Y-axis unit management in explorer section

[amlannandy]

• Keep the Y axis unit. Automatically populate it from metadata for single queries
• When there is no unit in metadata, and they give the Y axis unit from selector (ask them to save it to the metadata as well, provide the functionality for it as well)
• For multiple queries
  • When there is more than one metric with different units, enable one chart per metric unit by default (and disable one chart option)

[amlannandy]

PR is approved. But we will merge it along with the changes for this issue.
So marking it as blocked for now

[srikanthccv]

Complete now.