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

Don't use whole-archive linking (#71) ...

* First attempt at converting to OBJECT libraries.  Not working due to more object library limitations

* Only compile the main libraries as OBJECT, because that's all that CMake can be made to do right now.

* Fix availability of target-specific flags

* Missed some usages

* Fix some STM32 ethernet stuff that was not linking correctly

* More fixes for STM32 ethernet and weak symbols

* Fix prebuilt object file linking for MUSCA_S1

* Fix STM32 eth init license headers

Silence noisy print, fix bug with MBED upload method not working

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

Add in mbed-cmake's configuration generators

Add automatic execution of mbedtools configure

Fix memap not running

Add core flags dependency back to the target flags, making sure that the core flags headers actually work

Add default upload method configuration for each target, make greentea tests use cmake upload methods

Response to comments

Adapt mbed-cmake's automatic uploading and debugging system

Remove the legacy Mbed CLI 1 tools!

- Split mbed-core and mbed-rtos into -sources and -flags targets ...

- Fix some logic errors in top level cmakelists related to building greentea tests
- Fix mbed_create_distro() for OBJECT libraries

Write defines into a disk file instead of passing 100s of them on the command line directly. Fixes some issues with build commands on my machine, and makes it a lot easier to view the make VERBOSE=1 output.

Add mbed-create-distro

CMake: Enable improved armclang support in CMake 3.21 ...

CMake versions 3.20 and below always add compiler and linker flags
based on `CMAKE_SYSTEM_PROCESSOR`, for example `--cpu=Cortex-M33`.
This sometimes overrides flags we set in tools/cmake/cores/*.cmake
and results in link failure or unbootable binaries. To workaround
this, we added more linker flags to "counter" what CMake automatically
adds.

From CMake 3.21 onwards, CMake by default does not add flags to
armclang anymore, and it fully relies on projects to set all flags.
In this case we do not need to set `CMAKE_SYSTEM_PROCESSOR` or use
workarounds anymore. We still turn on workarounds when an older
version of CMake (3.19 and 3.20) is used, but in the future we might
require users to have at least CMake 3.21.

CMake: Move post build functions out of root CMakeLists.txt ...

The 'post build' functions are made visible by adding the mbed-os
subdirectory. This is not ideal as any components in mbed-os wishing to
call the functions must be added after the functions are defined. To
improve modularity move these functions to a separate CMake script.

We include the post build CMake script in app.cmake for now so we don't
break user's projects.

app.cmake: Replace tabs with spaces ...

The coding standards of Mbed OS require indentation of four spaces.

CMake: set CMAKE_MODULE_PATH in the Mbed OS CMakelists.txt ...

Update CMAKE_MODULE_PATH at once place.

Note, we update also CMAKE_MODULE_PATH in app.cmake. This is temporary until we get a proper way to include
Mbed Os (removing app.cmake need to be included by an application).

CMake: add mbed_ prefix to our CMake files ...

To avoid conflicts as we expose our CMake list files via CMAKE_MODULE_PATH. Some files already include it, this
aligns the rest of files.

I leave app.cmake as it is - it's user facing and it would be breaking change. We can clean this one for the next major version.

CMake app: add our cmake folder to CMAKE_MODULE_PATH ...

All files within tools/cmake can now include within tools/cmake. We do not expose
internal folders like core/profiles/toolchains.
They should be included via toolchain file (mbed_toolchain in our case).

CMake tools: use CMAKE_CURRENT_LIST_DIR instead of MBED_PATH ...

Excluding greentea tests, they will be fixed separately (more work needed).

Rebase against master

Whitespace formatting changes.

Add extra lines as requested

Parse requirements.txt in CMake

Add FindPythonPackage and use it to detect memap dependencies

Add newline

Set executable suffix in CMake

Rebase linker script change properly, re-add external toolchain file support