[Miosix][sbs] Upgrade to Miosix 2.7 and move BSPs to Boardcore

This MR accomplishes the following:

• Upgrade Miosix to version 2.7
  • Update usages of removed kernel functions to our own wrappers:
    • miosix::getTick()
    • miosix::Thread::sleepUntil()
    • miosix::Thread::IRQenableIrqAndTimedWaitMs
• BSPs of Skyward-made boards have been moved to the src/bsps directory, outside the kernel index, improving development comfort and iteration speed when modifying or introducing new BSPs. The build system has been updated to reflect this change.
• Miosix Host and MxGui dependencies have been updated with support for Miosix 2.7.