Use params for log messages

[matt-richardson]

The logging that comes out of WebJobs.Extensions.* mostly uses params for structured logging, but some spots just use plain old interpolated strings.

This means that it's hard to filter these out, as they're all different:

This PR updates the log messges so they use params better, like structured logs should be.

Note:

• I didn't update anything in the WebJobs.Extensions.CosmosDB namespace - As I dont use that, and am unsure of the details, I'm hesitant to change it
• Even though the general consensus is to use CamelCase for property names, I've followed the existing convention (functionName instead of FunctionName) for the properties