Function remap_streaming 

pub fn remap_streaming<'a, F>(
    mappings_iter: MappingsIter<'a>,
    sources: &[String],
    names: &[String],
    sources_content: &[Option<String>],
    ignore_list: &[u32],
    file: Option<String>,
    loader: F,
) -> SourceMap
where
    F: Fn(&str) -> Option<SourceMap>,

Streaming variant of remap that avoids materializing the outer map.

Accepts pre-parsed metadata and a MappingsIter over the outer map’s VLQ-encoded mappings. Uses StreamingGenerator to encode the result on-the-fly without collecting all mappings first.

Because MappingsIter yields mappings in sorted order, the streaming generator can encode VLQ incrementally, avoiding the sort + re-encode pass that remap requires.

The ignore_list from both upstream and outer maps is propagated. Invalid segments from the iterator are silently skipped.