Merge #108001

108001: kvcoord: test additional ambiguous failure states r=AlexTalks a=AlexTalks

This change builds on the testing introduced in #107323 with additional
subtests evaluating the behavior of different race outcomes with
contended transactions where the first transaction experiences an RPC
failure (i.e. an ambiguous write).

Depends on #107323, #108154.

Part of: #103817

Release note: None

Co-authored-by: Alex Sarkesian <[email protected]>