Function normalize_script 

pub fn normalize_script(input: &ScriptInput<'_>) -> IstanbulFileCoverage

Convert one V8 ScriptCoverage entry into an IstanbulFileCoverage.

Each V8 FunctionCoverage contributes one Istanbul function entry whose hit count is taken from the function’s first range (the outermost [startOffset, endOffset)). Block-level sub-ranges are deliberately not flattened into separate functions — that’s the closed-source three-state tracker’s job.