test(auth): fix OCPP spec references and remove duplicated tests

test(auth): fix OCPP spec references and remove duplicated tests

Replace incorrect G03/G04 (Change Availability) prefixes with correct
OCPP 2.0.1 Authorization section codes (C10/C11/C12/C13/C15).
Remove spec prefixes from internal tests with no direct spec mapping.

- C10.FR.01: cache all statuses (was G03.FR.01.T4)
- C10.FR.07: eviction mechanism (was G03.FR.01.T5)
- C10.FR.08: TTL/expiry behavior (was G03.FR.01.T6/T7)
- C11: cache invalidation (was G03.FR.01.004)
- C12: cache miss behavior (was G03.FR.01.002)
- C13.FR.01: local auth list priority (was G03.FR.01.T8)
- C15: offline authorization (was G03.FR.02)
- Remove 5 duplicated cache unit tests from integration suite
- Update TEST_STYLE_GUIDE.md examples