Function webext_storage::migration::do_insert

fn do_insert(
    tx: &Transaction<'_>, 
    ext_id: &str, 
    vals: Vec<(String, Value)>
) -> Result<usize>

Insert the extension and values. If there are multiple values with the same key (which shouldn't be possible but who knows, database corruption causes strange things), chooses an arbitrary one. Returns the number of entries inserted, which could be different from vals.len() if multiple entries in vals have the same key.