Function entry_field 

pub fn entry_field<'a>(
    entries: &'a [(Expr, Expr)],
    name: &str,
) -> Option<&'a Expr>

Look up an unqualified-keyed field in a map’s entry slice. The slice-level primitive field delegates to; use it when a caller already holds the &[(Expr, Expr)] entries (provider codecs, MCP) instead of rebuilding a map.