1139: Wdt config changes r=lulf a=huntc
Per commits:
* By passing WDT config around we can control it more easily and promote sharing it between files.
* The memory layout of the s140 crept into a number of memory files, which can cause confusion (well, it did for me!).
* Obtaining the current WDT config is useful so that we do not have to duplicate configurations around the place. A constructor method has been introduced that attempts to return the current running WDT config from the WDT peripheral. The bootloader example has also been updated to show how the watchdog can be obtained and used.
Co-authored-by: huntc <huntchr@gmail.com>
Compiler will infer a different lifetime for BootFlash than for the
borrowed flash, which makes it require more type annotations than if it
was just owning the type. Since it doesn't really matter if it owns or
borrows in practical use, change it to own so that it simplifies usage.
* Remove the need for generic const expressions and use buffers provided in the flash config.
* Extend embedded-storage traits to simplify generics.
* Document all public APIs
* Add toplevel README
* Expose AlignedBuffer type for convenience.
* Update examples
