Support legacy tool receipts with PEP 508 requirements (#5679)
## Summary
In #5494, I made breaking changes to the tool receipt format. This would
break existing tools for all users. This PR makes the change
backwards-compatible by supporting deserialization for the deprecated
format.
Closes https://github.com/astral-sh/uv/issues/5680.
## Test Plan
Beyond the automated tests, you can run `cargo run tool list` on your
existing machine.
Before:
```
warning: `uv tool list` is experimental and may change without warning
warning: Ignoring malformed tool `black` (run `uv tool uninstall black` to remove)
warning: Ignoring malformed tool `poetry` (run `uv tool uninstall poetry` to remove)
warning: Ignoring malformed tool `ruff` (run `uv tool uninstall ruff` to remove)
```
After:
```
warning: `uv tool list` is experimental and may change without warning
black v0.1.0
- black
poetry v1.8.3
- poetry
ruff v0.0.60
- ruff
```
