Teensy 4.1 port with Ethernet support (#144) ...

* Start porting to Teensy 4.1, also fix some compiler warnings in FSL HAL

* Add hardware init for Teensy, refactor phy drivers, rework IMX EMAC autonegotiate code

* Revert some testing changes

* Fix incorrect phy address used outside of low_level_init_successful()

* Ethernet operational!

* Turn off DEBUG_IMX_EMAC

* Style fixes

* Style again

* Bugfix: mbed_lib.json files in project source dir were not getting picked up

* Bugfix: CLion debug configurations not generated properly due to variables going out of scope

* Support Teensy OTP MAC address

(vscode + cmake) Add option MBED_GENERATE_VSCODE_CONFIG (#142)

Fix debug-less upload methods (#140) ...

* Fix debug-less upload methods

* Oops, fix build outside of Clion

Refactor upload methods to streamline the debugging experience (#129) ...

* Change all debug configurations to not reset and exit on error.  Initial tasks.json implementation.

* st-util working on command line and VS Code!

* Convert STM32CUBE, fix spaces in GDB server task command

* pyocd working!

* Convert OpenOCD

* Convert JLINK

* Convert REDLINK upload method

* Fix CMake typo

* Try and fix some variable scope issues

* Initial CLion implementation.  Need to test with hardware.

* Add a separate task that kicks off a build before each debug session

Switch to cortex-debug plugin for VS Code to improve debugging experience

Add in mbed-cmake's configuration generators