This CL implements a simulated FE process and a simulated BE service.
You can view their specific usage methods at
`fe/src/test/java/org/apache/doris/utframe/DemoTest.java`
At the same time, I modified the configuration of the maven-surefire-plugin plugin,
so that each unit test runs in a separate JVM, which can avoid conflicts caused by
various singleton classes in FE.
Starting a separate jvm for each unit test will bring about 30% extra time overhead.
However, you can control the number of concurrency of unit tests by setting the `forkCount`
configuration of the maven-surefire-plugin plugin in `fe/pom.xml`. The default configuration
is still 1 for easy viewing of the output log. If set to 3, the entire FE unit test run time is about
4 minutes.
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