feat(Timeline): add task date

[stonebuzz]

Add missing task date in the timeline display

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	#15657

[cedric-anne]

Honestly, I still do not understand what this date is. Indeed, this is neither the creation date (that is displayed in task header), neither the planned date. So what is it?

[stonebuzz]

Some use it this way

• A supervisor creates a task for a tech for a date, the tech schedules it according to his calendar (so not necessarily the same date)

• Creation of a task with this date (for info) without scheduling

• and certainly another use case

[orthagh]

After irl discussion:

• I'm not in favor of adding this in view (already too much overloaded)
• there is a misunderstanding of the purpose of the field, rename it, or better see if can be merged with other date field.
• target main