Move fail point structs to an internal package.

[matthewdale]

Summary

Move the mtest.FailPoint struct and the associated structs to a new internal package internal/failpoint.

Background & Motivation

Most fail points in Go Driver integration tests are defined using the mtest.FailPoint type. However, some integration tests, like TestConvenientTransactions, cannot use mtest because it creates an import cycle. We can move the FailPoint and associated structs to a separate internal package, allowing them to be used in any test package in the driver.

Note that the SetFailPoint function is intentionally not moved to the internal/failpoint package because that would require importing the mongo package, causing an import cycle in some cases.

[mongodb-drivers-pr-bot]

API Change Report

No changes found!