Custom lock-file serialization (#3909)
## Summary
This PR changes the lock-file format to use inline tables for wheels and
source distributions, which currently use separate tables that make the
file harder to follow.
```diff
[[distribution]]
name = "typing-extensions"
version = "4.10.0"
source = "registry+https://pypi.org/simple"
- [distribution.sdist]
- url = "https://files.pythonhosted.org/packages/16/3a/0d26ce356c7465a19c9ea8814b960f8a36c3b0d07c323176620b7b483e44/typing_extensions-4.10.0.tar.gz"
- hash = "sha256:b0abd7c89e8fb96f98db18d86106ff1d90ab692004eb746cf6eda2682f91b3cb"
- size = 77558
-
- [[distribution.wheel]]
- url = "https://files.pythonhosted.org/packages/f9/de/dc04a3ea60b22624b51c703a84bbe0184abcd1d0b9bc8074b5d6b7ab90bb/typing_extensions-4.10.0-py3-none-any.whl"
- hash = "sha256:69b1a937c3a517342112fb4c6df7e72fc39a38e7891a5730ed4985b5214b5475"
- size = 33926
+ sdist = { url = "https://files.pythonhosted.org/packages/16/3a/0d26ce356c7465a19c9ea8814b960f8a36c3b0d07c323176620b7b483e44/typing_extensions-4.10.0.tar.gz", hash = "sha256:b0abd7c89e8fb96f98db18d86106ff1d90ab692004eb746cf6eda2682f91b3cb", size = 77558 }
+ wheel = [{ url = "https://files.pythonhosted.org/packages/f9/de/dc04a3ea60b22624b51c703a84bbe0184abcd1d0b9bc8074b5d6b7ab90bb/typing_extensions-4.10.0-py3-none-any.whl", hash = "sha256:69b1a937c3a517342112fb4c6df7e72fc39a38e7891a5730ed4985b5214b5475", size = 33926 }]
```
The downside is that the inline-tables end up quite long and TOML
doesn't support line breaks in inline tables, yet.
Part of https://github.com/astral-sh/uv/issues/3611.
