feat: make hwinfo features modular

[aminya]

Fixes #94
Related to #54

Implements #94 (comment)

All components are available via the hwinfo::hwinfo target, or via individual CMake targets, which you can choose and link against depending on your needs.

target_link_libraries(your_target PRIVATE hwinfo::hwinfo)

or

target_link_libraries(
  your_target
  PRIVATE hwinfo::cpu
          hwinfo::gpu
          hwinfo::ram
          hwinfo::mainboard
          hwinfo::disk
          hwinfo::os
          hwinfo::battery)

The CMake options control which components will be built and available in the library:

• HWINFO_OS "Enable OS detection" (default to ON)
• HWINFO_MAINBOARD "Enable mainboard detection" (default to ON)
• HWINFO_CPU "Enable CPU detection" (default to ON)
• HWINFO_DISK "Enable disk detection" (default to ON)
• HWINFO_RAM "Enable RAM detection" (default to ON)
• HWINFO_GPU "Enable GPU detection" (default to ON)
• HWINFO_GPU_OPENCL "Enable usage of OpenCL in GPU information" (default to OFF)
• HWINFO_BATTERY "Enable battery detection" (default to ON)