[keyserver][lib] Blob client function to remove multiple holders

Summary:
Similiarly to assignMultipleHolders(), added a blob client function to remove multiple holders.
Added a keyserver wrapper for this function which provides HTTP headers with CSAT.

Test Plan: Called the function from keyserver against local Blob Service. Verified that requested holders were removed from DDB

Reviewers: kamil, tomek

Reviewed By: kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13511