fix: track elapsed_compute for file stream - #18752

> create external table customer 
stored as parquet
location '/Users/jizezhang/datafusion/benchmarks/data/tpch_sf1/customer';
0 row(s) fetched. 
Elapsed 0.026 seconds.

> explain analyze
select * from customer;
... elapsed_compute=8ns ...

> create external table customer 
stored as parquet
location '/Users/jizezhang/datafusion/benchmarks/data/tpch_sf1/customer';
0 row(s) fetched. 
Elapsed 0.033 seconds.

> explain analyze
select * from customer;
... elapsed_compute=1.786625ms ...