BB-11146: Write documentation for Webpack assets build (#21537)
BB-11146: Write documentation for Webpack assets build (#21537)

- improved documentation and changelog
- fixed typo in variable name
- renamed command class to match the name
- changed the structure of `assets.yml` file for management console to be the same as for store front
- removed unused fixtures from unit tests of LayoutBundle
orocrm/OroCalendarBundle,orocrm/OroCalendarBundle,orocrm/OroCalendarBundle