2200: Add Teensy 4 board r=bradjc a=mciantyre

### Pull Request Overview

The PR proposes Tock support for the Teensy 4. As of this PR, the Tock kernel, and a variety of small examples, can run on [Teensy 4.0][teensy40] and [Teensy 4.1][teensy41] development boards. The PR builds on the i.MX RT chip foundation added in #1918.

[teensy40]: https://www.pjrc.com/store/teensy40.html
[teensy41]: https://www.pjrc.com/store/teensy41.html

The board makes use of

- the LED on pin 13
- UART2 on pins 14 and 15
- GPT1 as an alarm

The Teensy 4 boards use i.MX RT **1062** chips. Given our current chip features, the 1060 chip family is identical to the 1050 chip family. Before integrating the Teensy 4 board, I *renamed `chips/imxrt1050` to `chips/imxrt10xx`*. I updated the `imxrt1050-evkb` board to use the renamed crate.

Additional changes to the i.MX RT chip crate include

- adding a LPUART2 peripheral
- renaming the `gpt1` module to `gpt`, and adding `GPT2`
- supporting periodic clock selection, allowing a user to select the static crystal oscillator as the GPT clock source

Changes to the chip crate should be backwards compatible for `imxrt1050-evkb` users. Let me know if we see an issue.

### Testing Strategy

I tested the PR by running `blink` and `console` libtock-c examples on both a Teensy 4.0 and 4.1 board. I repackaged the examples [here](https://github.com/mciantyre/tock-teensy4-apps).

The PR was **not** tested on an NXP i.MX RT 1050 evaluation board; I don't have that hardware.

### TODO or Help Wanted

This pull request may be tested on a 1050 evaluation board. @valexandru, if you have an opportunity to test this work and review these changes, I'd appreciate it!

This PR does not address any of the TODOs noted in #1918. In particular, the `imxrt10xx` chip still does not use the new peripheral instantiation approach (#2069). If this is still TODO and not urgent, I'm happy to support that cleanup in a separate PR.

This Teensy 4 support was based on a different chip implementation. That chip implementation supported DMA, and a UART driver that used DMA. If we see value in a DMA driver for i.MX RT chips, I'm happy to contribute the driver.

### Documentation Updated

- [x] ~~Updated the relevant files in `/docs`~~, or **no updates are required**

I've added documentation in `boards/teensy4`. The documentation

- lists the tools that you need to program a Teensy 4
- how to build the kernel and apps
- how to convert the program to a HEX file, which is necessary to program a board

### Formatting

- [x] Ran `make prepush`.

### New Platform Checklist

- [x] Hardware is widely available.
- [x] I can support the platform, which includes release testing for the platform, at least initially.
- Basic features are implemented:
  - [x] `Console`, including `debug!()` and userspace `printf()`.
  - [x] Timers.
  - [x] GPIO with interrupts.

I assume the basic chip features were provided by #1918. Let me know if we need to make all three features available through the board. As of this writing, the Teensy 4 board does not expose an input GPIO that responds to an interrupt.


2216: add 15.4 and ble to nano33ble r=bradjc a=hudson-ayers

### Pull Request Overview

This pull request adds the 15.4 and BLE drivers to the nano33ble, rather than leaving support as commented out, as the comments had already fallen out-of-date.


### Testing Strategy

BLE was tested using the `ble_advertising` and `ble_passive_scanning` apps in `libtock-c`.

15.4 was tested using the `radio_tx` and `radio_rx` apps in `libtock-c` and sending messages back and forth with an nrf52840-dk.

### TODO or Help Wanted

N/A

### Documentation Updated

- [x] No updates are required.

### Formatting

- [x] Ran `make prepush`.


Co-authored-by: Ian McIntyre <ianpmcintyre@gmail.com>
Co-authored-by: Hudson Ayers <hayers@stanford.edu>
Co-authored-by: Hudson Ayers <32688905+hudson-ayers@users.noreply.github.com>

2311: Board based instantiation of chip drivers and interrupt mappings: imxrt10xx r=bradjc a=mciantyre

### Pull Request Overview

The PR refactors the `imxrt10xx` chip and boards to support board-based initialization (first proposed in #2069). It builds on the work of #1918 and #2200, where we noted the effort as a TODO. After this PR, you may instantiate and configure i.MX RT peripherals in a board, or use the default peripherals provided by the chip.

Most peripherals were easily transitioned to the new API. The exception was the GPIO driver, which referenced `static` GPIO ports and pins throughout the code. I may have found some issues in the driver, so I took the refactoring opportunity to update the implementation, trying to follow [this suggestion](https://github.com/tock/tock/blob/master/chips/stm32f4xx/src/gpio.rs#L595). I'll leave more details in review comments.

Other changes include

- fix a GPT clock gating bug introduced in #2200
- move UART root clock initialization out of the `configure()` method, and into CCM peripheral setup

### Testing Strategy

Tested `boards/teensy40` on a Teensy 4.0 using the tests from #2200.

`boards/imxrt1050-evkb` continues to compile, but I don't have the hardware to test examples.

### TODO or Help Wanted

Looking for feedback on the refactor. Let me know if it deviates too much from the other chips.

Holding as draft to

- [x] ~~wait for #2310, since the new GPIO driver needs `min_const_generics`~~ accepting as-is, and we'll remove the feature later
- [x] figure out a way to remove the remaining `static` peripheral in `iomuxc_snvs`
- [x] remove `std` dependency in new unit tests, avoiding the conditional `no_std` in the crate
- [x] leave thoughts on GPIO changes
- [x] clean up commit messages

### Documentation Updated

- [x] ~~Updated the relevant files in `/docs`, or~~ no updates are required.

### Formatting

- [x] Ran `make prepush`.


Co-authored-by: Ian McIntyre <ianpmcintyre@gmail.com>