What this PR does:

1. Edit our update-deps.py script to generate output compatible with bzlmod instead of workspace, for our dependencies that are just http_archive. For example, dragonbox, ncrypto, simdutf.
2. Put a bunch of dependencies that got frozen back under automatic management.

What we can get Claude to do for us:

• Support dependencies that are taken directly from BCR. For example, ada-url, brotli.
• Support BCR dependencies with http_archive overrides. For example, sqlite3, highway.

To make it easier for our robot buddy to do this, I've added an unused function called get_bcr_version that I wrote back in August, as a starting point.

With these two elements added, we can add all of our dependency management workflows as of today.

Not addressed in this PR: our "shared_deps" system where the same version is used in edgeworker and workerd needs to be redone. With bzlmod we cannot load these things across repos, though I suspect we can with symlinks. We might need some help here. At worst we can just break the link between these versions and manage them independently.

Future work: I am still not sure if we want this, but it's certainly doable: Instead of using the separate jsonc files and generating Bazel code, we could parse the MODULE.bazel files. The potential advantages are a bit less conceptual complexity and getting ready for renovate when DEVTOOLS makes it available on GitHub. This can be figured out later and doesn't block any of this work.