Log4Net appender can't be configured to use a connection string

[johnendev]

Is your feature request related to a problem?
Yes. The Log4Net appender doesn't support connection strings. Only InstrumentationKey is available, which is obsolete.

Describe the solution you'd like.
Add a way to configure the connection string.

Describe alternatives you've considered.
Using InstrumentationKey for now but is no longer supported after March 31, 2025: https://learn.microsoft.com/en-us/azure/azure-monitor/app/connection-strings