[SPARK-53195][CORE] Use Java InputStream.readNBytes instead of ByteStreams.read

[dongjoon-hyun]

What changes were proposed in this pull request?

This PR aims to use Java 9+ InputStream.readNBytes API instead of ByteStreams.read.

Why are the changes needed?

To simplify the code by using native Java API.

- var numBytes = ByteStreams.read(gzInputStream, buf, 0, bufSize)
+ var numBytes = gzInputStream.readNBytes(buf, 0, bufSize)

Does this PR introduce any user-facing change?

No behavior change.

How was this patch tested?

Pass the CIs.

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

No.

[dongjoon-hyun]

Thank you, @yaooqinn .

[dongjoon-hyun]

For this single file change, I verified manually like the following.

$ dev/lint-scala
Using SPARK_LOCAL_IP=localhost
Scalastyle checks passed.
Scalafmt checks passed.

$ build/sbt "core/testOnly *.UtilsSuite"
...
[info] Run completed in 3 seconds, 97 milliseconds.
[info] Total number of tests run: 61
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 61, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.
[success] Total time: 20 s, completed Aug 8, 2025, 12:07:19 AM

[dongjoon-hyun]

Merged to master. Thank you, @yaooqinn and @peter-toth .