Turn CowOperationType into an enum

There's a bug previsouly where we compare return value of
GetCowOpSourceInfoData() with CowOperationType. Such bugs are possible
because cow operation enums are weakly typed integers. Turn
CowOperationType into strongly typed enum to prevent such bugs.

Test: th
Bug: 304602386
Change-Id: If6941a4740c374ed066cf0aee9e52f4df05a9b38
8 files changed