Improve Datetime and Daterange Views contextual grouped filter names

Problem/Motivation

When you create a contextual filter in Views for a datetime or daterange field, you see field like

node.field_date_only (full_date)
node.field_date_range:end_value (day)

for grouped filters. This is unintuitive and inconsistent with how other filed types are displayed, eg

Image (field_image:height)

Proposed resolution

Update datetime_type_field_views_data() to be consistent with other filter text, and build the title using the same method as views_field_default_views_data().

Remaining tasks

Patch
Add tests
Review
Up to date screenshots available from 'User interface changes'

User interface changes

TBA before and after screenshots

API changes

Data model changes