Rollup merge of #136031 - lqd:polonius-debugger-episode-1, r=compiler-errors

Expand polonius MIR dump

This PR starts expanding the polonius MIR:
- switches to an HTML file, to show graphs in the same document as the MIR dump, share them more easily since it's a single file that can be hosted as a gist, and also to allow for interactivity in the near future.
- adds the regular NLL MIR + polonius constraints
- embeds a mermaid version of the CFG, similar to the graphviz one, but that needs a smaller js than `dot`'s emscripten js from graphvizonline

[Here's an example](https://gistpreview.github.io/?0c18f2a59b5e24ac0f96447aa34ffe00) of how it looks.

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In future PRs: mermaid graphs of the NLL region graph, of the NLL SCCs, of the polonius localized outlives constraints, and the interactive polonius MIR dump.

r? ```@matthewjasper```

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