- Removed unneeded include
- Removed redundant check for blob_size

- Added unit tests for secret_store
- Added mock implementations for the ocalls and seal API
- Added trivial definitions of some open enclave types needed by the secret_store module

- Mock functions are now prefixed with `mock_` to follow the general pattern used for other HAL tests

- Mock implementation of functions needed by the tested unit are now part of the test suite, and just call the corresponding mock functions

- mocks no longer depend on specific definitions from secret_store
- now asserting that the expected values are written to the kvstore
- read/remove/exist tests now just write data interact directly to the kvstore and only test the read/remove/exist logic