CSHARP-5712: withTransaction API retries too frequently

[sanych-sun]

PR to implement RetryabilityHelper.GetRetryDelayMs. Please do not merge, depending on the comment/question in the Driver's PR:
mongodb/specifications#1862 (comment)

[Copilot]

Pull request overview

This PR implements the RetryabilityHelper.GetRetryDelayMs method to control retry delays with exponential backoff, addressing the issue of transactions retrying too frequently. The implementation adds jitter to prevent thundering herd problems and includes comprehensive parameter validation.

Key Changes

• Adds GetRetryDelayMs method with exponential backoff calculation and random jitter
• Removes unused MongoDB.Driver.Core.Connections import from test file
• Adds comprehensive test coverage for valid inputs, edge cases, and parameter validation

Reviewed changes

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

File	Description
src/MongoDB.Driver/Core/Operations/RetryabilityHelper.cs	Implements the core retry delay calculation with exponential backoff and jitter
tests/MongoDB.Driver.Tests/Core/Operations/RetryabilityHelperTests.cs	Adds unit tests for the new method and removes unused import

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[Copilot]

The calculation backoffInitial * Math.Pow(backoffBase, attempt - 1) may overflow for large attempt values, which would then be capped by Math.Min. Consider adding overflow protection or documenting the maximum safe attempt value to prevent unexpected behavior.

Suggested change

	return (int)(j * Math.Min(backoffMax, backoffInitial * Math.Pow(backoffBase, attempt - 1)));
	// compute the largest exponent such that backoffInitial * backoffBase^exponent <= backoffMax
	var maxExponent = Math.Log(backoffMax / (double)backoffInitial, backoffBase);
	var effectiveExponent = attempt - 1;
	double delayWithoutJitter;
	if (effectiveExponent >= maxExponent)
	{
	delayWithoutJitter = backoffMax;
	}
	else
	{
	delayWithoutJitter = backoffInitial * Math.Pow(backoffBase, effectiveExponent);
	}
	return (int)(j * delayWithoutJitter);

[Copilot]

Pull request overview

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

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[Copilot]

Creating a new Random instance for each call can lead to predictable values when called in quick succession due to time-based seeding. Consider using a static ThreadLocal instance for .NET Framework targets to ensure better randomness in concurrent scenarios.