The current shard role API is tested in one giant unit test  "shard_role_test.cpp" which is getting quite big to maintain or execute. 
This ticket proposes to split it into 3 subtests:

• one unit test for yielding and restoring
• one unit test for acquisitions specifically
• one unit test for acquisition on collections being resharded (new unit tests introduced by SERVER-111782)

The author of this ticket can eventually evaluate to split it into more tests if deemed valuable