[SPARK-51729] Support head/tail for DataFrame

[dongjoon-hyun]

What changes were proposed in this pull request?

This PR aims to support head/tail API for DataFrame.

Why are the changes needed?

For feature parity.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Pass the CIs and do the manual test.

$ swift test --filter DataFrameTests.head
...
􀟈  Test head() started.
􁁛  Test head() passed after 0.232 seconds.
􁁛  Suite DataFrameTests passed after 0.232 seconds.
􁁛  Test run with 1 test passed after 0.232 seconds.

$ swift test --filter DataFrameTests.tail
...
􀟈  Test tail() started.
􁁛  Test tail() passed after 0.229 seconds.
􁁛  Suite DataFrameTests passed after 0.229 seconds.
􁁛  Test run with 1 test passed after 0.229 seconds.

Was this patch authored or co-authored using generative AI tooling?

No.

[dongjoon-hyun]

Thank you, @viirya ! Merged to main.