Remove redundant subproject discovery

Previously, project.findProjectsUnderPath() searched for projects and subprojects under the given path. The problem with
this is that project.findSubprojects() uses project.findProjectsUnderPath() to detect subprojects, which resulted in
subproject duplicates. Making the project and subproject discovery distinct steps fixes this and also makes the code
easier to follow.

Author: per1234

project/project.go

@@ -75,7 +75,11 @@ func findProjects(targetPath *paths.Path) ([]Type, error) {
 		return nil, fmt.Errorf("specified path %s is not an Arduino project", targetPath)
 	}
 
-	foundProjects = append(foundProjects, findProjectsUnderPath(targetPath, configuration.SuperprojectTypeFilter(), configuration.Recursive())...)
+	foundParentProjects := findProjectsUnderPath(targetPath, configuration.SuperprojectTypeFilter(), configuration.Recursive())
+	for _, foundParentProject := range foundParentProjects {
+		foundProjects = append(foundProjects, foundParentProject)
+		foundProjects = append(foundProjects, findSubprojects(foundParentProject, foundParentProject.ProjectType)...)
+	}
 
 	if foundProjects == nil {
 		return nil, fmt.Errorf("no projects found under %s", targetPath)
@@ -84,7 +88,7 @@ func findProjects(targetPath *paths.Path) ([]Type, error) {
 	return foundProjects, nil
 }
 
-// findProjectsUnderPath finds projects of the given type and subprojects of those projects. It returns a slice containing the definitions of all found projects.
+// findProjectsUnderPath finds projects of the given type under the given path. It returns a slice containing the definitions of all found projects.
 func findProjectsUnderPath(targetPath *paths.Path, projectTypeFilter projecttype.Type, recursive bool) []Type {
 	var foundProjects []Type
 
@@ -99,8 +103,6 @@ func findProjectsUnderPath(targetPath *paths.Path, projectTypeFilter projecttype
 		}
 		foundProjects = append(foundProjects, foundProject)
 
-		foundProjects = append(foundProjects, findSubprojects(foundProject, foundProject.ProjectType)...)
-
 		// Don't search recursively past a project.
 		return foundProjects
 	}