Experimental embassy changes

[bugadani]

These changes build on embassy-rs/embassy#3593 and #2684

We now manage our own timer queues, which means that

• if there are multiple queues (with integrated-timers), we can use a priority-limited mutex. This means that higher priority executors don't get blocked by lower priority ones (except for Priority1 which may be blocked by the thread mode executor, but that's it).
• if there is only a single queue (integrated or generic), we use a max priority lock (same thing as above, but instead of a critical section we end up with a spin lock).
• the embassy-side changes mean processing the timer queue has a much lower overhead when using integrated timers.

Configuration-wise, users have the options to select between:

• N integrated queues (requires N alarms)
• 1 integrated queue
• generic timer queue (for RTIC, for example) - this is the default if integrated-timers is not set, but probably should be inverted at this point, or at least default to single-queue.
• The size of the generic queue is configurable using ESP_HAL_EMBASSY_GENERIC_QUEUE_SIZE