Re-export druid_shell::Scalable & remove to_px/to_dp helpers on Scale

[ForLoveOfCats]

This allows use-ing Scalable and thus various type's implementation of to_px ect

[cmyr]

@xStrom does this make sense as public API to you?

[ForLoveOfCats]

It kinda already is. Scale has the public and very confusingly named to_px which accepts a generic arg which impls Scalable before calling the argument's own to_px passing in the instance of Scale (Which does not work in application code due to being unable to bring Scalable into scope). I say it is confusingly named because for the types which implement Scalable their to_px functions convert themselves using the Scale passed in but this apparent helper function on Scale does the opposite by converting the argument using itself as the scale.

When I initially drafted this PR I hadn't looked into these functions to much but now after using this branch for my project and poking around I think that the helper function on Scale should be removed and simply use the methods on these Scalable types. (Which I'll do and force push to this PR if others agree) The alternative could be to rename the helper function but I'd argue that it has no reason to exist as it is a single line to invoke a different function which is part of a trait anyway

My specific use case of having this functionality provided to applications is that I'm using it to handle font size in a DPI aware way by converting to absolute pixel values.

[ForLoveOfCats]

I've removed the helper functions and corrected any callsites I could find with a quick grep. I decided to leave the px_to_dp* functions as despite not finding any places which call any of them they seem reasonable enough to exist on Scale as is. I expect the CI to probably fail on some non-GTK shell

[ForLoveOfCats]

After fixing the CI and fiddling with merge conflicts I think this is ready for a review. Thankfully removing those functions turned out to be a fairly small change

[luleyleo]

This seems reasonable to me. Just one nit about the changlog.

[ForLoveOfCats]

So none of the CI seems to be running and the changelog still has a merge conflict after manually fixing it so I'm just going to let this sit for a while and hope Github sorts itself out

[luleyleo]

I can't spot the changes made in #1081 so maybe those are missing?

[luleyleo]

Suggested change

	- `Scale::to_px` and `Scale::to_dp` ([#1075] by [@ForLoveOfCats])
	- `Scale::to_px` and `Scale::to_dp`. ([#1075] by [@ForLoveOfCats])

[luleyleo]

Suggested change

	- Re-export `druid_shell::Scalable` under `druid` namespace ([#1075] by [@ForLoveOfCats])
	- Re-export `druid_shell::Scalable` under `druid` namespace. ([#1075] by [@ForLoveOfCats])

[ForLoveOfCats]

GH claims there is only one conflict and it is the following

Combined with the CI bugging out I think that Github is being silly so I'm going to let this sit for a bit and see if it figures itself out

[ForLoveOfCats]

I managed to fix the merge conflict by just moving the conflicting line up a line, not ideal but better than screwing up the PR's git log. The CI also seems to be functioning again, not sure if the conflict was blocking the CI from running as I'm 90% sure that I've had PRs run CI with merge conflicts but I don't know if the CI runs on just the PR's branch or on the master branch w/ the PR merged which would cause it to be blocked 🤷

[xStrom]

Sorry for not taking a look sooner, but yeah I think this change is fine.