Plotters canvas scales incorrectly with hdpi awareness enabled

[evshiron]

[gabdube]

Will look into this.

[HareInWeed]

I think #210 might fix the issue, but it causes more problem. With some experiments, I found that layouts will be messed up if I enable the high-dpi feature and hdpi awareness at the same time. Maybe inlining high_dpi::physical_to_logical in &PlottersBackend::get_size is a better way to go.