Our unified test locations are inconsistent. This complicates non-manual validation and synchronization of our unified tests.

The following is not a unified test dir:

• https://github.com/mongodb/specifications/tree/master/source/bson-corpus/tests

The following are unified test dirs:

• https://github.com/mongodb/specifications/tree/master/source/client-side-operations-timeout/tests
• https://github.com/mongodb/specifications/tree/master/source/change-streams/tests/unified
• https://github.com/mongodb/specifications/tree/master/source/command-logging-and-monitoring/tests/monitoring
• https://github.com/mongodb/specifications/tree/master/source/command-logging-and-monitoring/tests/logging

Let's standardize on the following, and move all unified tests:

/source/<directory>/tests/unified

Subdirs like logging and monitoring would be placed under that unified directory.

Drivers that refer to the previous directories would need to update those paths (breaking changes would be evident in any such driver through failing automation; all or almost all drivers should be unaffected, since the process is generally manual).