This allows you to list and explore connected USB devices. It
only stubs out the methods to communicate to endpoints. That will
come in a follow up once TinyUSB has it. (It's in progress.)
Related to #5986
In #4683, tannewt noticed that uncrustify was not running on some
file in common-hal.
I investigated and found that it was not being run on a bunch of paths.
Rather than make incremental changes, I rewrote list_files to work
bsaed on regular expressions; these regular expressions are created from
the same git-style glob patterns.
I spot-checked some specific filenames after this change, and all looks good:
```
$ python3 tools/codeformat.py -v --dry-run tests/basics/int_small.py ports/raspberrypi/common-hal/pulseio/PulseIn.c extmod/virtpin.c tests/thread/thread_exit1.py ports/raspberrypi/background.h extmod/re1.5/recursiveloop.c
tools/codeformat.py -v --dry-run tests/basics/int_small.py ports/raspberrypi/common-hal/pulseio/PulseIn.c extmod/virtpin.c tests/thread/thread_exit1.py ports/raspberrypi/background.h extmod/re1.5/recursiveloop.c
uncrustify -c /home/jepler/src/circuitpython/tools/uncrustify.cfg -lC --no-backup extmod/virtpin.c ports/raspberrypi/background.h ports/raspberrypi/common-hal/pulseio/PulseIn.c
black --fast --line-length=99 -v tests/thread/thread_exit1.py
```
recursiveloop and int_small are excluded, while PulseIn, virtpin,
and background are included.
Testing running from a subdirectory (not _specifically_ supported though):
```
(cd ports && python3 ../tools/codeformat.py -v --dry-run raspberrypi/common-hal/pulseio/PulseIn.c ../extmod/virtpin.c)
../tools/codeformat.py -v --dry-run raspberrypi/common-hal/pulseio/PulseIn.c ../extmod/virtpin.c
uncrustify -c /home/jepler/src/circuitpython/tools/uncrustify.cfg -lC --no-backup ../extmod/virtpin.c raspberrypi/common-hal/pulseio/PulseIn.
```
As a side-effect, a bunch more files are re-formatted now. :-P
After this change, the following program works for me on the MIMXRT1010-EVK:
```python
import pwmio
import board
p = pwmio.PWMOut(board.D13, frequency=1_000_000, variable_frequency=True)
p.duty_cycle = 32868
while True:
pass
```
Querying and varying the duty_cycle and frequency work as well.
The lowest frequency obtainable is about 2kHz; there is an additional
divider which would allow lower PWM frequencies (I think 1kHz is important
for servos?)
Something odd happens with very low duty cycles, such as
```python
>>> p.frequency = 2000
>>> p.duty_cycle = 2
```
instead of a symmetrical waveform, it's asymmetrical. With `duty_cycle=4`,
the effect disappears. The reason for this is probably hidden in the
datasheet, but could affect servos or other things that count pulse
widths.
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.
