Omnichannel Version update to 3.20.6

Improvement & New Feature:

• Support Download a new variant from an existing product in the channel

• Tidying up Flush Cache UI

  

We just revamped our Flush channel page to make it easier to understand and use

• Group multiwarehouse outlets in Different Inventory page

• Add multiwarehouse support in API/v1/POSAccount/GetByDomain (cherry-picked)

Bug Fixes (cherry-picked):

• Fix filter menu order for multiwarehouse

• Fix Different inventory error

• Fix filter differently when outlet not found

• Fix different inventory page - show inventory even if the outlet is null