Issue 4938 - fix race conditions related to LazyFileSystem

The main point here is in the adding of the scheduler dependency to LazyFileSystem which by default executes tasks immediately. It allows to control the execution of file system tasks by accumulating of pending ones and executing them one by one until the desired state is reached as well as check the state between tasks. It also gets rid of any threads what simplifies the debugging and eliminates a possibility for race conditions.
In order to simplify the creation of FilterEngine using custom scheduler there is a helper method
`FilterEnginePtr CreateFilterEngine(LazyFileSystem& fileSystem, const JsEnginePtr& jsEngine, const FilterEngine::CreationParameters& creationParams = FilterEngine::CreationParameters());`. All places where it's actually used are accordingly changed.

[sergei, 2017-07-27 09:15:32]

https://codereview.adblockplus.org/29499583/diff/29499584/test/FilterEngine.cpp
File test/FilterEngine.cpp (left):

https://codereview.adblockplus.org/29499583/diff/29499584/test/FilterEngine.c...
test/FilterEngine.cpp:65:
std::this_thread::sleep_for(std::chrono::milliseconds(100));
Since there is no class waiting for its internal threads it was already no the
issue #5198, however this sleep might was required to allow FileSystem finish
running operations. Now it may be removed.

https://codereview.adblockplus.org/29499583/diff/29499584/test/FilterEngine.c...
test/FilterEngine.cpp:594:
std::this_thread::sleep_for(std::chrono::milliseconds(200));
#4937 is also fixed now

[hub, 2017-07-27 12:42:02]

LGTM