Histogram: Add support for stacking mode

[adela-almasan]

Histogram stacking mode

histo_stacking.mov

Migration

histo_stacking_migrate.mov

Fixes #38047

Please check that:

• It works as expected from a user's perspective.
• If this is a pre-GA feature, it is behind a feature toggle.
• The docs are updated, and if this is a notable improvement, it's added to our What's New doc.

[codeincarnate]

I'm not sure I can comment on all of this, but tested it out and worked fine.

Did make me curious how we're doing stacking order with histogram. It appears right now we're not re-ordering based on query order which I think is supposed to happen. But that can be done elsewhere 😄

[leeoniya]

It appears right now we're not re-ordering based on query order which I think is supposed to happen.

there's no re-ordering. it stacks in order of the data, bottom up. the only way to change this is to reorder in the query or in a transform.