feat(calendar): clipped text for static calendars

[LuLaValva]

• This PR contains CSS changes
• This PR does not contain CSS changes

Description

A few minor clean-up changes that were noticed during review of the date input on eBayUI:

• span should now have full support for aria-disabled so there is no need for the calendar__cell--disabled class
• In the static calendar, aria-label is replaced with an additional clipped span
• There is now indication that a button is active (I opted for bolded text, this may be debated in the comments)

Checklist

• I verify the build is in a non-broken state
• I verify all changes are within scope of the linked issue

• I regenerated all CSS files under dist folder
• I tested the UI in all supported browsers
• I did a visual regression check of the components impacted by doing a Percy build and approved the build
• I tested the UI in dark mode and RTL mode
• I added/updated/removed Storybook coverage as appropriate

[LuLaValva]

Thanks for the comments Ian, I think I've addressed everything that you pointed out

[ianmcburnie]

Last changes needed:

For interactive, move aria-current onto the button.
For non-interactive, replace aria-current on td with clipped text in span.

[LuLaValva]

Thanks for the quick reviews Ian, much appreciated

[ianmcburnie]

Thanks Luke! You have the patience of a saint :-)

[LuLaValva]

Ok, here's a summary of the changes made here that need to be reflected in ebayui-core.

All calendar cells:

• td that used aria-selected="true" now uses class="calendar__cell--selected", and (configurable) "selected" text must be added to the aria-label of buttons or to the clipped text of spans.

Interactive calendar cells:

• Move aria-current="date" from td to button

Static calendar cells:

• all aria labels should be moved to clipped text
• td aria-current="date" > span `##`
  should be transformed to
  td > span.calendar__cell--current `##` > span.clipped ` - [configurable text]`
  where the default text is "today"
• Spans with the calendar__cell--disabled class should have configurable clipped text that defaults to "inactive"