Makefile.features: add a common file for the features parsing

[cladmi]

Contribution description

This will allow sharing it between Makefile.include and
makefiles/info-global.inc.mk.

Also some common variables definition can also be moved to here.

Part of moving CPU/CPU_MODEL definition to Makefile.features to have it
available before Makefile.include.

Next steps

• Base the pull requests for migrating CPU/CPU_MODEL onto this one
• Move the definition of FEATURES_MISSING/FEATURES_USED/FEATURES_OPTIONAL_USED/FEATURES_CONFLICTING to this file instead of duplicating it

Testing procedure

Features are still parsed, so any example with required features still list the same output like for example

make --no-print-directory -C tests/periph_hwrng/ info-boards-supported
acd52832 airfy-beacon arduino-due b-l072z-lrwan1 b-l475e-iot01a calliope-mini cc2538dk esp32-mh-et-live-minikit esp32-olimex-evb esp32-wemos-lolin-d32-pro esp32-wroom-32 esp32-wrover-kit esp8266-esp-12x esp8266-olimex-mod esp8266-sparkfun-thing f4vi1 firefly frdm-k22f microbit msbiot mulle native nrf51dk nrf51dongle nrf52832-mdk nrf52840-mdk nrf52840dk nrf52dk nrf6310 nucleo-f207zg nucleo-f410rb nucleo-f412zg nucleo-f413zh nucleo-f429zi nucleo-f722ze nucleo-f746zg nucleo-f767zi nucleo-l053r8 nucleo-l073rz nucleo-l432kc nucleo-l433rc nucleo-l452re nucleo-l476rg nucleo-l496zg openmote-b openmote-cc2538 pba-d-01-kw2x pic32-wifire pyboard reel remote-pa remote-reva remote-revb ruuvitag stm32f429i-disc1 stm32f4discovery stm32f769i-disco stm32l476g-disco thingy52 ublox-c030-u201 udoo yunjia-nrf51822

Issues/PRs references

It is part of

• Makefile.features: prerequisites for moving CPU/CPU_MODEL to boards/Makefile.features Makefile.features: prerequisites for moving CPU/CPU_MODEL to boards/Makefile.features #11478
• Tracking: move CPU/CPU_MODEL to Makefile.features Tracking: move CPU/CPU_MODEL to Makefile.features #11477

[jcarrano]

Tested info-boards-supported still works.

[cladmi]

Thanks for the review