fix: tree-style explain for memory table shows wrong row count

[2010YOUY01]

Which issue does this PR close?

• Closes #.

Rationale for this change

See reproducer in datafusion-cli, the rows:1 line in the explain is the wrong result, it should be total rows for the memory table (101)

yongting@Yongtings-MacBook-Pro-2 ~/C/datafusion (main>)> datafusion-cli
DataFusion CLI v54.1.0
> create table test_memtable as
select *
from generate_series(100);
0 row(s) fetched.
Elapsed 0.004 seconds.

> explain format tree select * from test_memtable;
+---------------+-------------------------------+
| plan_type     | plan                          |
+---------------+-------------------------------+
| physical_plan | ┌───────────────────────────┐ |
|               | │       DataSourceExec      │ |
|               | │    --------------------   │ |
|               | │        bytes: 65632       │ |
|               | │       format: memory      │ |
|               | │          rows: 1          │ |
|               | └───────────────────────────┘ |
|               |                               |
+---------------+-------------------------------+
1 row(s) fetched.
Elapsed 0.001 seconds.

What changes are included in this PR?

fix the explain for row count

Are these changes tested?

sqllogictest

Are there any user-facing changes?

[2010YOUY01]

Those small formatting changes are enforced by cargo test --test sqllogictests -- --complete

We can keep them here, and future auto-fixes won't need to change again.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.27%. Comparing base (f1f0449) to head (d75e726).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24511      +/-   ##
==========================================
- Coverage   81.27%   81.27%   -0.01%     
==========================================
  Files        1116     1116              
  Lines      395017   395078      +61     
  Branches   395017   395078      +61     
==========================================
+ Hits       321055   321101      +46     
- Misses      55166    55179      +13     
- Partials    18796    18798       +2     

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[nuno-faria]

Thanks @2010YOUY01.