Rollup merge of #128353 - ferrocene:jonathanpallant/add-dependencies-to-copyright-file, r=Kobzol

Change generate-copyright to generate HTML, with cargo dependencies included

`x.py run generate-copyright` now produces `build/COPYRIGHT.html`. This includes a new format for in-tree dependencies, and also adds out-of-tree cargo dependencies.

After consulting expert opinion, I have elected to include every top-level:

* `*NOTICE*`
* `*AUTHOR*`
* `*LICENSE*`
* `*LICENCE*`, and
* `*COPYRIGHT*` file I can find - case-insensitive.

This is because the cargo package metadata's `author` field is not a list of copyright holders and does not meet the requirements of the Apache-2.0 license (which says you must include a NOTICE file with the binary if one was supplied by the author) nor the MIT license (which says you must include 'the above copyright notice').

I believe it would be appropriate to include this file with every Rust release, in order to do an even better job of appropriately recognising the efforts of the authors of the first-party and third-party libraries we are using here.

The output includes something like 524 copies of the Apache-2.0 text because they are not all identical. I think I count about 50 different variations by shasum - some differ in whitespace, while some have the boilerplate block at the bottom erroneously modified (don't modify the copy in the license, modify the copy you paste into your own source code!). Running `gzip` on the HTML file largely makes this problem go away, and the average browser is far happier with a ~6 MiB HTML file than the average Markdown viewer is with a ~6 MiB markdown file. But, if someone wants to, do they could submit a follow-up which de-dups the license text files and adds back-links to earlier identical copies (for some value of 'identical copy').

```console
$ xpy run generate-copyright
$ cd build
$ gzip -c COPYRIGHT.html > COPYRIGHT.gz
$ xz -c COPYRIGHT.html > COPYRIGHT.xz
$ ls -lh COPYRIGHT.*
-rw-r--r--  1 jonathan  staff   241K 29 Jul 17:19 COPYRIGHT.gz
-rw-r--r--@ 1 jonathan  staff   6.6M 29 Jul 11:30 COPYRIGHT.html
-rw-r--r--  1 jonathan  staff    59K 29 Jul 17:19 COPYRIGHT.xz
```

Here's an example [COPYRIGHT.gz](https://github.com/user-attachments/files/16416147/COPYRIGHT.gz).

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