* Adjust definition to make the default constructor `constexpr`.
This permits use in classes that want lazy initialization and their
own `constexpr` constructor, such as `mstd::mutex`.
* Add `get_no_init()` method to allow an explicit optimisation for
paths that know they won be the first call (such as
`mstd::mutex::unlock`).
* Add `destroy()` method to permit destruction of the contained object.
(`SingletonPtr`'s destructor does not call its destructor - a cheat
to omit destructors of static objects). Needed if using in a class
that needs proper destruction.
We will provide documentation how to create your own VirtualWatchdog. It's simple,
create timeout and watchdog objects.
This class brought lot of discussion and questions. After our refactor we made this class
just a linked list of objects - something tickers can do as well (they already have linked list) and handling hw should be
done via Watchdog due to the limitations (timeout can be set only once per app!).
Watchdog can handle callbacks - VirtualManager can attach to the tick. This should simplify the logic.
Watchdog can tick on its own using tickers.
VirtualWatchdog uses attach to get a callback when Watchdog ticks - to process own
linked list of virtual watchdogs.
Watchdog should be usable on it's own - kicking it via ticker. No Virtual involved.
VirtualWatchdog as well - services should use this one to have multiple one in the system.
There's WatchdogManager - basically internal class to manage ticker for Watchdog.
Refactor old Watchdog (it was not a driver) to become VirtualWatchdog.
This is software virtual watchdog. This it the primary used watchdog in user application.
VirtualWatchdog: has-a watchdog. Initializes hw watchdog - start it when first used, stops it when there is no more VirtualWatchdog in the system -
list is empty.
Adding also check to watchdog to make sure there is only one in the system - runtime error if multiple objects created to already
running hw watchdog.
Watchdog is hardware driver. It interacts with HAL - provides wrapper to interact with the peripheral.
Provides basic functionality: start/stop, get timeout/max timeout.
It is automatically kicked by a timer, according to the timeout set in ctor.