Add a common logger interface

This MR adds the following:

1. A common interface that supports collecting information to meet observability/monitoring requirements. This interface provides methods to log traces at various severity levels (i.e. info, warning, error), audit events and dependencies. The specific implementations of this interface have the freedom to choose how and where to store the logs.

2. An implementation of the interface that logs to Application Insights using a Log4J2 appender and the SLF4J API. Traces are logged using the SLF4J-provided info, warn and error methods. Exceptions are automatically forwarded to the "exceptions" Application Insights table.

Example usage:

ICoreLogger logger = CoreLoggerProvider.getInstance().getLogger(SomeClass.class);
logger.info("Log this message");