Let context/initiate.log[Timing]Measurement(...) be available from ContextLocal.

[stolsvik]

This would be a way to "sub-divide" a stage's time use into its separate operations. The most typical would be queries.

Also make this available from ContextLocal.

Extra-timings should be made available through the Interceptor API.

[stolsvik]

I had evidently forgotten this case when making #45, which is identical - and closed by 84ba574
So, I'll reuse this for what I had forgotten there: Make it available from ContextLocal.