[lib] Use batch Blob service endpoints in processHolders action

Summary:
Address ENG-9355.
When processing holders, we can make 1-2 batch Blob HTTP calls instead of M+N calls for every single processed holder.

Depends on D13656

Test Plan: Start a DM thread, set image thread avatar, then reset back to emoji. With Redux devtools and console logs verify that actions are successful.

Reviewers: kamil, tomek

Reviewed By: kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13657