Updated OpenTelemetry tests to use their own `SpanExporter` rather than depend on the `InMemorySpanExporter`.

[LarryOsterman]

When discussing the recent break with the OpenTelemetry folks, they rather strongly recommended that I stop using the InMemorySpanExporter type (which apparently is an internal test hook).

This change updates the OpenTelemetry test collateral to use a custom SpanExporter used by the tests.

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[LarryOsterman]

Ping :).

[LarryOsterman]

Ping2 :)