Summary

Implementation of the multilayer time axis, based on the timeslip prototype

Details

Some of the things still to do:

• API: add config option to switch on/off the multilayer axis (thanks Marco for your commit for this)
• UX bug: under some circumstances, missing ticks on the right edge of the time domain
• UX issue: avoid rendering the rightmost tick label if it would breach the right edge of the Cartesian projection area (we may also have an option for rendering it if there's margin space)
• UX issue: add a couple of time rasters for the decades (it's unlikely but many-year timelines need it), with/without labeled years
• UX issue: solve the returing axis tick duplication on a couple of mocks
• UX issue: append st/nd/rd/th to day-of-month numbers
• UX issue: properly varying the tick lengths to match the timeslip prototype and avoid overlap of labels with ticks
• UX issue: clearer hierarchy of grid line saliency similar to timeslip
• UX issue: top placed multilayer axis
• UX issue: less contrasty grid lines and smaller contrast (luma) differences between different time granularities
• UX issue: sparser ticks/gridlines 1: ticks/gridlines should be no denser than bin width (minimum interval) of data
• UX issue: sparser ticks/gridlines 2: chart width dependent minimum allowed tick pixel distance
• UX issue: theme integration and ensuring layer and theme dependent tick lengths (or lack thereof), grid saliency etc. into the options as a quick and dirty data propagation, it should be reworked
• testing: as a test, run all image tests that have a time axis with this option on, so we can analyze the image diffs for odd cases
• testing: fix up unit tests, some of which got commented out in the previous PR
• testing: ensuring that time zones get handled correctly
• testing: addition of VRT cases for the various time resolutions (quite a few zoom levels from ms to decades, not all covered yet)
• implementation detail: cleaning up visible_ticks.ts (remove temp ts-ignores etc.)
• implementation detail: in a follow-up PR, unify the new timeslip chrono with your former timeslip chrono

Issues

Closes #1310
Fixes #929
Fixes #908

Checklist

• The proper chart type label has been added (e.g. :xy, :partition)
• The proper feature labels have been added (e.g. :interactions, :axis)
• The :theme label has been added and the @elastic/eui-design team has been pinged when there are Theme API changes
• All related issues have been linked (i.e. closes #123, fixes #123)
• New public API exports have been added to packages/charts/src/index.ts
• Unit tests have been added or updated to match the most common scenarios
• The proper documentation and/or storybook story has been added or updated
• The code has been checked for cross-browser compatibility (Chrome, Firefox, Safari, Edge)
• Visual changes have been tested with all available themes including dark, light, eui-dark & eui-light