Add GenAI core package

[LittleLittleCloud]

We are excited to review your PR.

So we can do the best job, please check:

• [x] There's a descriptive title that will make sense to other developers some time from now.
• [x] There's associated issues. All PR's should have issue(s) associated - unless a trivial self-evident change such as fixing a typo. You can use the format Fixes #nnnn in your description to cause GitHub to automatically close the issue(s) when your PR is merged.
• [x] Your change description explains what the change does, why you chose your approach, and anything else that reviewers should know.
• [ ] You have included any necessary tests in the same PR.

7169 Task 2

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 68.67%. Comparing base (8e3f72d) to head (e39c8fc).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #7177 +/- ## ========================================== - Coverage 68.67% 68.67% -0.01% ========================================== Files 1263 1263 Lines 257955 257955 Branches 26698 26698 ========================================== - Hits 177148 177140 -8 - Misses 73994 74001 +7 - Partials 6813 6814 +1 ``` | [Flag](https://app.codecov.io/gh/dotnet/machinelearning/pull/7177/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | Coverage Δ | | |---|---|---| | [Debug](https://app.codecov.io/gh/dotnet/machinelearning/pull/7177/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | `68.67% <ø> (-0.01%)` | :arrow_down: | | [production](https://app.codecov.io/gh/dotnet/machinelearning/pull/7177/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | `62.93% <ø> (-0.01%)` | :arrow_down: | | [test](https://app.codecov.io/gh/dotnet/machinelearning/pull/7177/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | `88.88% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet#carryforward-flags-in-the-pull-request-comment) to find out more. [see 3 files with indirect coverage changes](https://app.codecov.io/gh/dotnet/machinelearning/pull/7177/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet)