Add new tool for tailing logs

We should considering adding a new tool (`dotnet logs`) to our suite of existing diagnostic tools that allows you to connect to and tail logs from an existing process that utilizes `Microsoft.Extensions.Logging` as the logging library.

While it is already possible to collect logs via `dotnet trace` by enabling the appropriate provider, there is no way to immediately consume these logs for ad-hoc analyses. Similar to `dotnet counters`, this tool will enable ad-hoc investigations by providing a textual-output to the console.

All ASP.NET Core/Worker application in 3.0 have an EventSource sink for ILogger already wired up in the default host and should benefit from this without the need to instrument the end user's code.

Goals with this tools:

1. Ability to tail logs without the need to modify existing user code.
2. Support configurable (and reloadable) log verbosity