Fix `RandomAccessFile#skipBytes(int)` and overhaul associated tests.
### Testing notes
`SkipBytes` has gone through a major facelift.
- Past EOF `getFilePointer()` check was broken, fixed in f15ccfaf.
- `new RandomAccessFile("input.txt" , "rw")` was not working at all. File
needed to be passed via `new File(System.getProperty("test.src", "."),
"input.txt")`. Fixed in f4300dbb.
- `input.txt` doesn't need to be VCS-tracked. Removed it in f4300dbb.
- Extended the tests to reproduce the issue, see 049ae7c5. New cases are cloned
from 46d34868 delivered in [JDK-8394316].
- Migrated the tests to JUnit, see 02ac947c.
[JDK-8394316]: https://bugs.openjdk.org/browse/JDK-8394316
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Commit messages:
- Migrate `SkipBytes` to JUnit
- Fix `RandomAccessFile`
- Extend tests to reproduce the issue
- Fix `input.txt` read
- Fix past EOF `getFilePointer()` check in the test
Changes: https://git.openjdk.org/jdk/pull/33649/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=33649&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8396040
Stats: 271 lines in 4 files changed: 144 ins; 124 del; 3 mod
Patch: https://git.openjdk.org/jdk/pull/33649.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/33649/head:pull/33649
PR: https://git.openjdk.org/jdk/pull/33649
