Remove unused headers in servers

[YYF233333]

Followup #100564

Cleanup includings in servers/, remove unused headers, replace headers used for transitive include, move headers down in the include chain if possible.

[akien-mga]

Seems like modules/camera/camera_feed_linux.cpp needs to include RenderingServer, and for some reason there's a new warning in an iOS file triggered by these changes (likely a pre-existing warning that just happened to be raised now because some header changes caused recompilation of the cached object).

platform/ios/keyboard_input_view.mm:187:27:{187:25-187:26}{187:29-187:87}: error: comparison of integers of different signs: 'NSInteger' (aka 'long') and 'unsigned long' [-Werror,-Wsign-compare,2]
                for (NSInteger i = 0; i < MIN([substringToDelete length], [substringToEnter length]); i++) {
                                       ~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[akien-mga]

Looks good! Could you squash the commits? See PR workflow for instructions.

[YYF233333]

Sorry, left for a while. Squashed.

[akien-mga]

BTW, I'd be interested in knowing your workflow for identifying these unused headers.

I've tried to use iwyu for this exact use case in the past, but I could only get it to add includes that are used through existing explicit includes (which would bloat things considerably, as we tend to expect that including e.g. node_2d.h is sufficient and you don't need also explicit canvas_item.h, node.h, object.h, etc.). But indeed a "don't-include-what-you-don't-use" is sorely needed for C/C++ codebases.

Edit: Closed by mistake.

[YYF233333]

BTW, I'd be interested in knowing your workflow for identifying these unused headers.

Actually clangd is enough for identifying unused header. Everytime I open a file in vscode there are unused header warnings which is annoying and finally I decide to clean up them.

iwyu gives some more aggressive suggestions, like replace some headers with forward declarations.
e.g.

core/os/memory.h should add these lines:
#include "core/typedefs.h"            // for _FORCE_INLINE_, _ALWAYS_INLINE_
template <typename T> class SafeNumeric;

core/os/memory.h should remove these lines:
- #include <type_traits>  // lines 39-39
- #include "core/templates/safe_refcount.h"  // lines 35-35

I'm currently evaluating how much build time they can save, and may pick some big improvements (if there are any) without sacrificing readability.

[akien-mga]

Thanks!