Offers and items in promotions (RTC-32125)

New read only field - 'Offer ID' is visible in the details of an existing offer. If the user collapse the details of an offer, the field is still visible. When creating new offer this field appears after saving this new offer.
There is a new column named 'OFFER ID' in 'Items in promotions' view ('Items list' and 'Item group list') and in 'Promotion offers' view.

Performance of adding items to offer group (RTC-32248)

Improved performance of adding items to offer group. Improved performance of fetching data for 'Items in promotions' page.