[new-core-alignment] service includes cleaned up

[rex-schilasky]

Description

Service header clean up, see see eclipse-ecal/ecal-core#15.

Based on changes by @FlorianReimold):

I tried to apply the IWYU pragma. I mainly focused on std headers, as those don't come with umbrella headers.

Cherry-pick to

• None

[KerstinKeller]

👍
I think if we do cleanup like this, we should try to come up with a rule, e.g. first include your own header (e.g. client_session.cpp first include is client_session.h, then all standard headers, then all other thirdparty headers, and then all needed ecal headers?

Not 100% sure, but I would mix it like in server_manager.h 😄

[FlorianReimold]

I usually include the class declaration .h (in cases of .cpp) first, then stl headers, then custom headers. But in this case it took a considerable amount of time to just go through the clang-tidy output and decide for each warning if I wanted to apply the fix or not (there were a couple thousand warnings).
And as the order of includes are not supposed to matter anyways, I just clicked the fix-it checkboxes. I think the manual labor of re-sorting this is not worth the time, I would rather merge this and then further improve the includes. I am certain that I missed a lot of includes that should be there and I didn't fix any unnecessary includes, yet (i.e. remove them). A further improvement would also be to mark umbrella headers accordingly with an IWYU export comment.

[KerstinKeller]

I think, for eCAL6 we should think about getting rid of "umbrella headers". Yes it's nice that you can just include ecal.h and you get everything that you want, but is it necessary?