JAVA-5950 Update Transactions Convenient API with exponential backoff on retries

[nhachicha]

JAVA-5950

[Copilot]

Pull request overview

This PR implements exponential backoff with jitter for transaction retries in MongoDB's withTransaction convenience API. The implementation adds a configurable backoff mechanism that applies delays between retry attempts when transient transaction errors occur, following the MongoDB specification with a growth factor of 1.5 for transactions.

Key Changes

• Introduces ExponentialBackoff utility class with factory methods for transaction retries (5ms base, 500ms max, 1.5x growth) and command retries (100ms base, 10s max, 2.0x growth)
• Integrates backoff logic into ClientSessionImpl.withTransaction() to delay between retry attempts
• Adjusts test configuration to verify backoff behavior with multiple retry attempts

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
driver-core/src/main/com/mongodb/internal/ExponentialBackoff.java	New utility class implementing exponential backoff with jitter using ThreadLocalRandom
driver-sync/src/main/com/mongodb/client/internal/ClientSessionImpl.java	Adds backoff delay before transaction retries and uses CSOT timeout when available
driver-core/src/test/unit/com/mongodb/internal/ExponentialBackoffTest.java	Comprehensive unit tests validating backoff calculations, growth factors, and maximum caps
driver-sync/src/test/functional/com/mongodb/client/WithTransactionProseTest.java	New functional test verifying exponential backoff behavior and adjusted existing test configuration

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[Copilot]

The test verifies the retry count but does not validate that exponential backoff delays are actually applied. Consider measuring elapsed time and asserting minimum expected delays to ensure backoff is functioning correctly. For example, with 3 retries at delays of ~5ms, ~7.5ms, and ~11.25ms, the total elapsed time should be at least the sum of minimum expected delays.