minify and filter embed managed pythons json on compile time (#12967)

## Summary

In #10939 I added the generated
`crates/uv-python/src/download-metadata-minified.json` file which is a
minified version of `crates/uv-python/download-metadata.json`.

The main reason for this PR is to avoid bloating the git objects as this
is a single-line file.

As a bonus, I also filtered the embed json to include only the versions
for the compiled target. Which should improve the binary size and
performance by a bit.

## Test Plan

<!-- How was it tested? -->

crates/uv-python/build.rs

@@ -0,0 +1,41 @@
+use std::fs;
+use std::path::Path;
+
+fn process_json(data: &serde_json::Value) -> serde_json::Value {
+    let mut out_data = serde_json::Map::new();
+
+    if let Some(obj) = data.as_object() {
+        for (key, value) in obj {
+            if let Some(variant) = value.get("variant") {
+                // Exclude debug variants for now, we don't support them
+                if variant == "debug" {
+                    continue;
+                }
+            }
+
+            out_data.insert(key.clone(), value.clone());
+        }
+    }
+
+    serde_json::Value::Object(out_data)
+}
+
+fn main() {
+    let version_metadata = Path::new("download-metadata.json");
+    let target = Path::new("src/download-metadata-minified.json");
+
+    let json_data: serde_json::Value = serde_json::from_str(
+        #[allow(clippy::disallowed_methods)]
+        &fs::read_to_string(version_metadata).expect("Failed to read download-metadata.json"),
+    )
+    .expect("Failed to parse JSON");
+
+    let filtered_data = process_json(&json_data);
+
+    #[allow(clippy::disallowed_methods)]
+    fs::write(
+        target,
+        serde_json::to_string(&filtered_data).expect("Failed to serialize JSON"),
+    )
+    .expect("Failed to write minified JSON");
+}