ProjectExplorer: Simplify use of AbstractProcessStep::init()

1. Systematically check for AbstractProcessStep::init() first in
   derived classes.
2. Use setupProcessParameters(processParameters()); by default in
   the base implementation.
3. Drop all re-implementations that are effectively the same.

Change-Id: I0ae54dd4909b354672a63ee56d0b7c2ea0732494
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/nim/project/nimcompilerbuildstep.cpp

@@ -202,16 +202,6 @@ QVariantMap NimCompilerBuildStep::toMap() const
     return result;
 }
 
-bool NimCompilerBuildStep::init()
-{
-    if (!AbstractProcessStep::init())
-        return false;
-
-    setupProcessParameters(processParameters());
-
-    return true;
-}
-
 void NimCompilerBuildStep::setBuildType(BuildConfiguration::BuildType buildType)
 {
     switch (buildType) {