FetchContent + VisualStudio miss google test header files in the generated project files

### Describe the issue

I use googletest with FetchContent and my main development environment is VisualStudio IDE - in the generated solution I can see gtest (and gtest_main) generated projects and I can see googletest source files (*.cc in Source Files) in these projects. Should I also see the header files like gtest.h in these projects (in Header Files)?

Should there be an entry in the googletest CMakeLists.txt for target_sources (of these header files) - I think that would instruct cmake to generate the Header Files entry in the generated project files.

### Steps to reproduce the problem

in the consuming CMakeLists.txt
...
include(FetchContent)

set(BUILD_GMOCK Off) # I am not sure if this meant to be used outside of googletest

FetchContent_Declare(
googletest
GIT_REPOSITORY https://github.com/google/googletest.git
GIT_TAG v1.17.0
)

FetchContent_MakeAvailable(googletest)
...

...
target_link_libraries(${PROJECT_NAME} PRIVATE
xyz
GTest::gtest_main
)
...

### What version of GoogleTest are you using?

1.17 (latest)

### What operating system and version are you using?

Windows 11 (latest)

### What compiler and version are you using?

VisualStudio (latest)

### What build system are you using?

What ever is bundled with the VisualStudio

### Additional context

_No response_

Start with the googletest CMakeLists.txt and reproduce the FetchContent setup from the issue using Visual Studio's generated solution. Check how the gtest and gtest_main targets list source and header files; done means the expected headers appear in the generated project files without breaking the targets.

Written by the indexing model from the issue text.