Refactor code for insert in sqllogictest

[xudong963]

Which issue does this PR close?

Follow up: #4496

Rationale for this change

What changes are included in this PR?

Refactor some code by review suggestions

Are these changes tested?

Are there any user-facing changes?

[xudong963]

Checked in my local, and it works

[insert.slt] Running query: "insert into users select * from users;"
thread 'main' panicked at 'explicit panic', datafusion/core/tests/sqllogictests/src/insert/mod.rs:48:21
stack backtrace:
   0: rust_begin_unwind
             at /rustc/96ddd32c4bfb1d78f0cd03eb068b1710a8cebeef/library/std/src/panicking.rs:575:5
   1: core::panicking::panic_fmt
             at /rustc/96ddd32c4bfb1d78f0cd03eb068b1710a8cebeef/library/core/src/panicking.rs:65:14
   2: core::panicking::panic
             at /rustc/96ddd32c4bfb1d78f0cd03eb068b1710a8cebeef/library/core/src/panicking.rs:114:5
   3: sqllogictests::insert::insert::{{closure}}
             at ./tests/sqllogictests/src/insert/mod.rs:48:21
   4: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/96ddd32c4bfb1d78f0cd03eb068b1710a8cebeef/library/core/src/future/mod.rs:91:19
   5: sqllogictests::run_query::{{closure}}
             at ./tests/sqllogictests/src/main.rs:151:53
   6: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/96ddd32c4bfb1d78f0cd03eb068b1710a8cebeef/library/core/src/future/mod.rs:91:19
   7: <sqllogictests::DataFusion as sqllogictest::runner::AsyncDB>::run::{{closure}}
             at ./tests/sqllogictests/src/main.rs:48:47

[alamb]

LGTM

[alamb]

Thanks @xudong963

[ursabot]

Benchmark runs are scheduled for baseline = e056a5c and contender = 4f7b003. 4f7b003 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-datafusion-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java