feat: report kernel bot upload results

[drbh]

this PR implements two release upload features that build on recent kernel-builder changes.

first, it uses the --create-pr flag added in huggingface/kernels#694 when a kernel uploads to a Hub repo outside kernels-community. this lets CI upload kernels like MiniMaxAI/msa and sgl-project/sgl-flash-attn3 by opening Hub PRs instead of assuming we can push directly.

second, it uses the upload json output added in huggingface/kernels#716 so each build can write its upload result, the workflow can aggregate the results after the matrix completes, and the kernel bot can update its existing comment with the Hub repo / Hub PR links.

the main plumbing is:

• resolve upload args from build.toml, using --create-pr for external repos and --repo-id for community repos
• write kernel-builder upload --output-json results as short lived workflow artifacts
• pass the kernel bot comment id through dispatch and update that comment from report-status
• use the external Hub repo ids for msa and sgl-flash-attn3

added script usage

this script checks if the build should be a PR or not and creates the args needed to be passed to the upload command

uv run .github/scripts/hub_pr_upload_args.py upload-args msa kernels-community

outputs

--create-pr

and this script reads the json output and structures it into text that is appended to the kernel bot's last comment

uv run .github/scripts/format_hub_upload_comment.py msa kernels-community '{"pull_requests":[{"url":"https://hf.co/kernels/MiniMaxAI/msa/discussions/1"}]}'

outputs

Hub uploads:
- Hub repo: https://huggingface.co/kernels/MiniMaxAI/msa
- Hub pull request: https://hf.co/kernels/MiniMaxAI/msa/discussions/1

also ran the dispatch/pr bot tests, yaml parsing, py_compile, and diff whitespace checks.

TLDR; this PR improves uploads to respect creating PR's and better reporting on the results

[sayakpaul]

Very cool!

@vasqu FYI. I think we should also do the same for #1010

[sayakpaul]

(nit): Possible to include an actual representative example?