Related to #45060
Refactor segment loading architecture to make segments autonomously
manage their own loading process, moving the orchestration logic from Go
(segment_loader.go) to C++ (segcore).
**C++ Layer (segcore):**
- Added `SetLoadInfo()` and `Load()` methods to `SegmentInterface` and
implementations
- Implemented `ChunkedSegmentSealedImpl::Load()` with parallel loading
strategy:
- Separates indexed fields from non-indexed fields
- Loads indexes concurrently using thread pools
- Loads field data for non-indexed fields in parallel
- Implemented `SegmentGrowingImpl::Load()` to convert and load field
data
- Extracted `LoadIndexData()` as a reusable utility function in
`Utils.cpp`
- Added `SegmentLoad()` C binding in `segment_c.cpp`
**Go Layer:**
- Added `Load()` method to segment interfaces
- Updated mock implementations and test interfaces
- Integrated new C++ `SegmentLoad()` binding in Go segment wrapper
---------
Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>
0a208d7224