Keycache test fixes

[bigbrett]

Fixes use of uninitialized variable as buffer size in/out argument, which caused sporadic test failures on hardware platforms

[Copilot]

Pull Request Overview

This PR stabilizes key cache tests by fixing uninitialized buffer-size usage, unifying key ID initialization, and improving cleanup logic to avoid sporadic failures.

• Initialize keyId to a defined erased constant rather than arbitrary literals
• Set exportedKeySize before each export call to ensure correct buffer length
• Refine eviction cleanup to handle both success and error paths and update error messages

Comments suppressed due to low confidence (1)

test/wh_test_crypto.c:972

• [nitpick] The message "after cache" may be confusing—consider "after caching key" or "after cache operation" for clarity on where it failed.

                    WH_ERROR_PRINT("Failed to export key after cache: %d\n",