The HID descriptor reported by circuitpython erroneously limited the
maximum keycode to 101, which prevented circuitpython from sending a
number of otherwise valid keycodes.
Closes#274
Introduces a way to place CircuitPython code and data into
tightly coupled memory (TCM) which is accessible by the CPU in a
single cycle. It also frees up room in the corresponding cache for
intermittent data. Loading from external flash is slow!
The data cache is also now enabled.
Adds support for the iMX RT 1021 chip. Adds three new boards:
* iMX RT 1020 EVK
* iMX RT 1060 EVK
* Teensy 4.0
Related to #2492, #2472 and #2477. Fixes#2475.
It was intended that the `f.load_glyphs` line was fast and did most of
the work. However, it actually didn't, because it's necessary to pass
in a code point by number, not by string.
Additionally, a little light layer violation is needed to make the check
for missing characters fast. This used to be less important, as no
fonts had missing characters. However, it would take an appreciable
length of time on the Korean translation when failing to find hundreds
of different code points.
Testing performed: built
build-circuitplayground_express_displayio/autogen_display_resources.c with ko
translation before and after change. verified the file content was identical.
Time went from about 7s on my machine to way under 1 second.
In cases where more than one board is connected to a single computer it can become pretty hard to figure out which board you're actually talking to. For example, if you have several MIDI-compatible boards they all show up as "CircuitPython MIDI". This change allows boards to replace the "CircuitPython" part of their USB descriptors with more specific text, for example, "CircuitPython Feather" or just "Feather". This will let folks more easily tell boards apart.
The new option is named `USB_INTERFACE_NAME` and is available in `mkconfigboard.mk`. For example:
```
USB_INTERFACE_NAME = "Feather"
```
