Run examples with and without authentication

[Alexey Palazhchenko]

We should run java-example, dotnet-example (and other examples like python-example once we have them) both with authentication enabled and disabled.

The easiest solution could be to pass the full MongoDB URI as a command-line argument instead of using hard-coded values:

• https://github.com/FerretDB/java-example/blob/6c92a3820d0ffd7afa1de8be4ca23433a8e1a677/java/src/main/java/com/start/Connection.java#L13
• https://github.com/FerretDB/dotnet-example/blob/4c18bfa1ba68ba4a9f70e2f795243d6aa32ee92f/Program.cs#L4

[Alexey Palazhchenko]

@b1ron PRs in example repos are merged