Clang from apt doesn't install on ubuntu:resolute

When trying to install clang 22 from the apt.llvm.org repo, it fails due to libxml2 not being available:

```
18.42 E: Unable to satisfy dependencies. Reached two conflicting assignments:
18.42 1. clang-tools-22:amd64=1:22.1.8~++20260613092238+e80beda6e255-1~exp1~20260613092253.78 is selected for install
18.42 2. clang-tools-22:amd64=1:22.1.8~++20260613092238+e80beda6e255-1~exp1~20260613092253.78 Depends libxml2 (>= 2.7.4)
18.42 but none of the choices are installable:
18.42 [no choices]
```

Start by reproducing the clang 22 installation failure on ubuntu:resolute using the apt.llvm.org repository. Inspect the dependency metadata for clang-tools-22 and libxml2 to identify why no installable libxml2 choice is available; done when the package installation succeeds on ubuntu:resolute.

Written by the indexing model from the issue text.