Refactor load service, remove seg manager

internal/core/src/segcore/segment_c.cpp

internal/querynode/client/client.go

internal/querynode/collection_replica.go

internal/querynode/load_service.go

internal/querynode/load_service_test.go

internal/querynode/param_table.go

internal/querynode/param_table_test.go

internal/querynode/query_node.go

internal/querynode/query_node_test.go

internal/querynode/segment.go

internal/querynode/segment_manager.go

internal/querynode/segment_manager_test.go