DirtyValue: add possibility to mark DirtyValue updated

[ljahn]

Adds the ability to manually mark a DirtyValue as updated.

This simplifies situations where a the user (or any other condition) selects if a value should be updated.

Example: In my Star Trek watch face I give the possibility to show weather or not. Using this function, I do not have to duplicate the weather updating code to the button press handler or introduce another variable weatherNeedsUpdate. I can just make the corresponding element visible, mark the weather data as updated (although it really isn't), and the next normal refresh loop will put the correct weather information.

[github-actions]

Build size and comparison to main:

Section	Size	Difference
text	372816B	0B
data	948B	0B
bss	22536B	0B

[mark9064]

I don't love this conceptually as it kind of breaks the idea that the DirtyValue is a state container that informs of updates only on state changes. However, I'm not dead set on not including this

For your use-case, could you update the weather irrespective of whether it's visible or not?