[fix][connector-mango] fix split with avgSize zero error

[CosmosNi]

fix split with AvgSize zero
close #9245

Purpose of this pull request

Does this PR introduce any user-facing change?

How was this patch tested?

Check list

• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• If you are contributing the connector code, please check that the following files are updated:
  1. Update plugin-mapping.properties and add new connector information in it
  2. Update the pom file of seatunnel-dist
  3. Add ci label in label-scope-conf
  4. Add e2e testcase in seatunnel-e2e
  5. Update connector plugin_config
• Update the release-note.

[Copilot]

Pull Request Overview

This pull request fixes a division by zero issue in the MongoDB connector's split logic when the average document size (AvgSize) is zero.

• Adds tests to cover scenarios where AvgSize is zero with and without documents.
• Updates the SamplingSplitStrategy to handle avgSize of zero without throwing an exception.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
seatunnel-connectors-v2/connector-mongodb/src/test/java/org/apache/seatunnel/connectors/seatunnel/mongodb/source/split/SamplingSplitStrategyTest.java	Adds tests for zero avgSize scenarios
seatunnel-connectors-v2/connector-mongodb/src/main/java/org/apache/seatunnel/connectors/seatunnel/mongodb/source/split/SamplingSplitStrategy.java	Adds condition to handle avgSize <= 0 and prevent division by zero

[Copilot]

Consider revising the condition to explicitly check for avgSize == 0 if negative values for avgSize are not expected. If negative avgSize could occur, it may be indicative of invalid data and should be handled appropriately.

Suggested change

	if (avgSize <= 0) {
	if (avgSize == 0) {