Add mdspan API to raft IVF functions

[lowener]

This PR changes the raft ivf function calls from raw pointer to mdspan. These functions are pre-compiled in libraft so it will speed up the compile time.

To receive the latest libraft release, it is recommended to use conda package manager:

conda install -c rapidsai -c nvidia -c rapidsai-nightly libraft==23.04.00a

I'm open for suggestions on how to handle installing conda and linking to libraft.
issue: #857

[sre-ci-robot]

Welcome @lowener! It looks like this is your first PR to milvus-io/knowhere 🎉

[mergify]

@lowener Please associate the related issue to the body of your Pull Request. (eg. “issue: #”)

[Presburger]

This PR changes the raft ivf function calls from raw pointer to mdspan. These functions are pre-compiled in libraft so it will speed up the compile time.

To receive the latest libraft release, it is recommended to use conda package manager:

conda install -c rapidsai -c nvidia -c rapidsai-nightly libraft==23.04.00a

I'm open for suggestions on how to handle installing conda and linking to libraft.

thanks for contribute the code,
is it heavily dependent on to the conda?

[lowener]

Conda is the preferred way to get libraft usually. Since conda is not being used right now I found an alternative with pip through the pylibraft package.

[Presburger]

@lowener Essentially, we are using knowhere more as a c++ library, and if he needs to rely on the python environment, it will be troublesome for us in the vast majority of cases.

[Presburger]

@lowener This pr is excellent and I would accept it if you remove the HINT_LIBRAFT related code. thank you.

[Presburger]

/lgtm

[Presburger]

/approve

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lowener, Presburger

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [Presburger]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment