Substrait physical plan producer emits invalid URIs for LocalFiles

[benbellick]

The Substrait physical plan producer emits bare paths instead of valid URIs for LocalFiles items.

datafusion/datafusion/substrait/src/physical_plan/producer.rs

Lines 65 to 67 in 1f26716

	path_type: Some(PathType::UriPath(
	file.object_meta.location.as_ref().to_string(),
	)),

This produces paths like path/to/file.parquet instead of proper URIs like file:///path/to/file.parquet.

These bare paths fail Url::parse() with "relative URL without a base" since they're not valid URIs per RFC 3986.