Core: Fix ByteBufferInputStream.read() to return -1 at EOF

[sachinnn99]

Fixes #16127.

SingleBufferInputStream.read() and MultiBufferInputStream.read() throw EOFException when the stream is exhausted. This violates the java.io.InputStream contract, which requires the no-arg read() to return -1 at EOF.

The multi-byte read(byte[], int, int) in both classes already correctly returns -1 at EOF — the two overloads were inconsistent.

Changes:

• SingleBufferInputStream.read(): return -1 instead of throwing EOFException
• MultiBufferInputStream.read(): return -1 at both EOF entry points instead of throwing EOFException
• Update testReadByte() to assert -1 return (including idempotency check)

Other EOFException-throwing methods (slice(), sliceBuffers(), skipFully()) are unchanged — they request specific byte counts where EOFException is the correct signal.