Move architecture and operating system probing to Python (#2381)

The architecture of uv does not necessarily match that of the python
interpreter (#2326). In cross compiling/testing scenarios the operating
system can also mismatch. To solve this, we move arch and os detection
to python, vendoring the relevant pypa/packaging code, preventing
mismatches between what the python interpreter was compiled for and what
uv was compiled for.

To make the scripts more manageable, they are now a directory in a
tempdir and we run them with `python -m` . I've simplified the
pypa/packaging code since we're still building the tags in rust. A
`Platform` is now instantiated by querying the python interpreter for
its platform. The pypa/packaging files are copied verbatim for easier
updates except a `lru_cache()` python 3.7 backport.

Error handling is done by a `"result": "success|error"` field that allow
passing error details to rust:

```console
$ uv venv --no-cache
  × Can't use Python at `/home/konsti/projects/uv/.venv/bin/python3`
  ╰─▶ Unknown operation system `linux`
```

I've used the [maturin sysconfig
collection](855f6d2cb1/sysconfig)
as reference. I'm unsure how to test these changes across the wide
variety of platforms.

Fixes #2326

crates/uv-dev/src/compile.rs

@@ -1,7 +1,6 @@
 use std::path::PathBuf;
 
 use clap::Parser;
-use platform_host::Platform;
 use tracing::info;
 use uv_cache::{Cache, CacheArgs};
 use uv_interpreter::PythonEnvironment;
@@ -21,8 +20,7 @@ pub(crate) async fn compile(args: CompileArgs) -> anyhow::Result<()> {
     let interpreter = if let Some(python) = args.python {
         python
     } else {
-        let platform = Platform::current()?;
-        let venv = PythonEnvironment::from_virtualenv(platform, &cache)?;
+        let venv = PythonEnvironment::from_virtualenv(&cache)?;
         venv.python_executable().to_path_buf()
     };