feat: registered EscapeHexCellWriteHandler in DefaultWriteHandlerLoader for XLSX

[delei]

Purpose of the pull request

Closed: #850

What's changed?

• Moved EscapeHexCellWriteHandler to org.apache.fesod.sheet.write.handler.impl package
• Registered EscapeHexCellWriteHandler in DefaultWriteHandlerLoader for XLSX format.

Checklist

• I have read the Contributor Guide.
• I have written the necessary doc or comment.
• I have added the necessary unit tests and all cases have passed.

[nkuprins]

You should also probably update the comment in EscapeHexCellWriteHandler on 39-43: "This handler is not registered by default..."

[nkuprins]

Not sure if you considered this already, but the handler isn't idempotent, so this PR affects the users who already register the handler themselves. Therefore, maybe it'd be good to make sure the handler can only take effect once per value.

[delei]

Not sure if you considered this already, but the handler isn't idempotent, so this PR affects the users who already register the handler themselves. Therefore, maybe it'd be good to make sure the handler can only take effect once per value.

A very good point. Thank you for pointing out the issue.

I have corrected this. This handler really should ensure that you only execute it once.

fesod/fesod-sheet/src/main/java/org/apache/fesod/sheet/write/metadata/holder/AbstractWriteHolder.java

Lines 448 to 461 in cbe4d8e

	Set<String> alreadyExistedHandlerSet = new HashSet<>();
	List<WriteHandler> cleanUpHandlerList = new ArrayList<>();
	for (Map.Entry<Integer, List<WriteHandler>> entry : orderExcelWriteHandlerMap.entrySet()) {
	for (WriteHandler handler : entry.getValue()) {
	if (handler instanceof NotRepeatExecutor) {
	String uniqueValue = ((NotRepeatExecutor) handler).uniqueValue();
	if (alreadyExistedHandlerSet.contains(uniqueValue)) {
	continue;
	}
	alreadyExistedHandlerSet.add(uniqueValue);
	}
	cleanUpHandlerList.add(handler);
	}
	}