fix: track elapsed_compute for file stream

[jizezhang]

Which issue does this PR close?

Address elapsed_compute baseline metrics not counting issue mentioned in #18195.

Before

> 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 ...

After

> 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 ...

Rationale for this change

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?