bump xitdb to 0.42.0

[xeubie]

This update brings a variety of improvements:

• Rollback works on a full disk, because setLength discards buffered data instead of flushing it
• Buffered writes are faster: sequential writes stay buffered after a flush, and the file length is cached between flushes
• The header is re-read and validated before top-level data is initialized, so another instance's data can't be overwritten
• Large files are handled correctly: reads more than 2 GiB before the buffer, and transfers of arrays near 2 GiB, no longer overflow an int
• Disk I/O uses positional FileChannel reads and writes in 1 MiB chunks, and flush writes straight from the backing array without copying it
• close closes the file even if the flush fails
• RandomAccessMemory has positional writeAt and readAt for the buffered file, and copies with System.arraycopy