Improve "no job functions found" error

[mattchenderson]

The warning that is logged when no job functions are found provides a few different, non-exhaustive options for remediation:

azure-webjobs-sdk/src/Microsoft.Azure.WebJobs.Host/Executors/JobHostContextFactory.cs

Line 161 in bb79ef3

startupLogger?.LogWarning($"No job functions found. Try making your job classes and methods public. {Resource.ExtensionInitializationMessage}");

azure-webjobs-sdk/src/Microsoft.Azure.WebJobs.Host/Properties/Resource.resx

Lines 126 to 128 in bb79ef3

	<data name="ExtensionInitializationMessage" xml:space="preserve">
	<value>If you're using binding extensions (e.g. Azure Storage, ServiceBus, Timers, etc.) make sure you've called the registration method for the extension(s) in your startup code (e.g. builder.AddAzureStorage(), builder.AddServiceBus(), builder.AddTimers(), etc.).</value>
	</data>

In some cases (such as Functions or when organization wrap WebJobs for multiple projects), it isn't actionable. This needs to be revised to provide clearer, better help. The system should log what extensions it did find. It should not provide specific code to be added, at least not in all cases, as the user may not control the extension registration directly, for example.