do not use default project to fix IDEA-194554 AE at com.intellij.codeInsight.documentation.DocumentationManager.assertSameProject

fix PsiTestUtil.removeContentEntry to remove the content entry with the given root, not just any entry containing it

Problem is that modal task doesn't mean that another modal task cannot be run in parallel.
As our tasks call invokeAndWait, some another UI events can be processed and as result, `closeProjectAndShowWelcomeFrameIfNoProjectOpened` will be called several times

Accordingly to JLS 8.8.9 default constructor is implicitly declared if there are no constructor declarations. If the superclass doesn't have an accessible no-arg constructor, it'll be a compile-time error which shouldn't bother those who tries to use the derived class.

This also fixes incorrect behavior when super-class declares package-private constructor (IDEA-208482).

Now it checks classes even if they don't have plugin.xml files in their modules, don't report error if an element and its class are declared in different modules included into the same plugin (IDEA-208472), show name of problematic class in error message, check serviceInterfaces attributes unless service is marked with 'overrides'.

for example, git-branches popup of IDEA-project has thousands of items

This reverts commit 4a04dbe3

fall back to some other color scheme

EnhancedSwitchMigrationInspection: generate assignment if declaration is not previous statement: IDEA-208192

* add module level items (`module` prefix).
* add extensions (with level prefix, e.g. `appExtensions`).
* add total number of plugins, components and services (`stats`).