This PR adds Customer Managed Encryption Keys (CMEK) support to the
StorageV2 FFI layer, enabling data encryption/decryption through the
cipher plugin system.
Changes:
- Add ffi_writer_c.cpp/h with GetEncParams() to retrieve encryption
parameters (key and metadata) from cipher plugin for data encryption
- Extend GetLoonReader() in ffi_reader_c.cpp to support CMEK decryption
by configuring KeyRetriever when plugin context is provided
- Add encryption property constants in ffi_common.go for writer config
- Integrate CMEK encryption in NewFFIPackedWriter() to pass encryption
parameters to the underlying storage writer
issue: #44956
Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>