support "int8" as a new data type in hnsw

[inabao]

Is your feature request related to a problem? Please describe.
Currently, vsag does not support any data types other than float32 (e.g., int8). I hope to add support for other data types.

Describe the solution you'd like
Next, I will demonstrate how to construct and search for an index that supports the int8 data type as expected.
build process

auto hnsw_build_paramesters = R"(
{
    "dtype": "int8",
    "metric_type": "l2",
    "dim": 128,
    "hnsw": {
        "max_degree": 16,
        "ef_construction": 100
    }
}
)";
auto index = vsag::Factory::CreateIndex("hnsw", hnsw_build_paramesters).value();
auto base = vsag::Dataset::Make();
base->NumElements(num_vectors)->Dim(dim)->Ids(ids)->Int8Vectors(vectors)->Owner(false);
index->Build(base);

search process

auto hnsw_search_parameters = R"(
{
    "hnsw": {
        "ef_search": 100
    }
}
)";
int64_t topk = 10;
auto query = vsag::Dataset::Make();
query->NumElements(1)->Dim(dim)->Int8Vectors(query_vector)->Owner(true);
auto result = index->KnnSearch(query, topk, hnsw_search_parameters).value();

How to do
I will complete the above feature through the following PR：

• support int8 for hnsw #65

Note: Currently, int8 is only supported for the IP metric.