Moved mtb-libs to lib submodule.

[jaenrig-ifx]

• mtb-libs directory moved to a new repo:
  https://github.com/Infineon/mtb-micropython-psoc6-port-integration
• The repository is now added as submodule in the lib/ dir
• Path modifications in Makefiles, make-pins.py (there were modifications as well in the mtb-libs scripts and makefiles).
• Now make submodules is required before mtb_init target.

[jaenrig-ifx]

@NikhitaR-IFX please check if these changes break in any way the deepcraft build flow. If so we have to reconsider them.

[github-actions]

Code size report:

   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +0 +0.000% PYBV10
     mimxrt:    +0 +0.000% TEENSY40
        rp2:    +0 +0.000% RPI_PICO_W
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS
  qemu rv32:    +0 +0.000% VIRT_RV32

[NikhitaR-IFX]

Deepcraft flow is unaffected. It works fine... Nice! :)