Add/Update logging in static files middleware

[rynowak]

From offline logging discussion:

Add Verbose logging where it can be useful for debugging

• Time box to 2 dev-days maximum (across all of k-core)
• Use EventIds at each logging statement
• Update any existing logging to include an EventId

Relevant logging points we want to include for sure:

        - Served a file - Information
        - Did not serve a file

[rynowak]

/cc @muratg

[muratg]

@Tratcher Looks like a good suggestion. Want to take a stab at very early RC1?

[Tratcher]

Did not serve a file would fire for almost every request, sounds like it should be verbose or debug. @rynowak Any examples of work already done that uses EventIds?

[rynowak]

Yes, not-serving a file would be Verbose.