Consolidate TriggerDetails log message into FunctionStarted message details

Having these two messages separately creates double the log messages in our hottest paths. Combining them together would save a lot of log capacity for us and customers.

Requires a design -- main goal is to get our backend kusto logs reduced, so it may be reasonable to do this *only* for our internal logs in some fancy way inside the `SystemLogger`. Other alternative is to change it for all customers at the source.

Log source: https://github.com/Azure/azure-webjobs-sdk/blob/6fa7fd7e373758c5a3948eada4fcfdb4a2dff2f7/src/Microsoft.Azure.WebJobs.Host/Loggers/FunctionInstanceLogger.cs#L22-L37

Start with src/Microsoft.Azure.WebJobs.Host/Loggers/FunctionInstanceLogger.cs at lines 22-37 and trace how TriggerDetails and FunctionStarted messages are emitted. Compare the internal and customer logging paths before choosing an approach. Done means the design is settled and the duplicate hot-path log output is reduced without losing required details.

Written by the indexing model from the issue text.