Load logger and test configuration from the classpath.

We currently only load log4j2-test.xml/test.properties from the ignite config directory. These files are not included in the test jar.
This is very inconvenient for modules that use the Ignite test framework (extensions, for the most part).

Suggestion:

1. include log4j2-test.xml and test.properties into test jar.
2. if log4j2-test.xml/test.properties was not found in ignite config directory - load them from the classpath.