Don't slice a sliced blob (#36866)

When slicing a blob that is already sliced we should reference it's
parent's data instead of creating a subview into the sliced blob. This
keeps the blob ancestry chain small and reduces the number of blobs that
we have to resolve.

Testing: Includes a new crashtest
Fixes: https://github.com/servo/servo/issues/36843

[try
run](https://github.com/simonwuelker/servo/actions/runs/14844873660)

---------

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

components/net/fetch/methods.rs

@@ -737,7 +737,7 @@ impl RangeRequestBounds {
             RangeRequestBounds::Final(pos) => {
                 if let Some(len) = len {
                     if pos.start <= len as i64 {
-                        return Ok(pos.clone());
+                        return Ok(*pos);
                     }
                 }
                 Err("Tried to process RangeRequestBounds::Final without len")