Implement UI scaling and more (#501)

**New Features**
 * Runtime font accessors and new symbol fonts for text, launcher, statusbar, and shared icons.
 * Added font height base setting to device.properties
 * Text fonts now have 3 sizes: small, default, large

**Improvements**
 * Renamed `UiScale` to `UiDensity`
 * Statusbar, toolbar and many UI components now compute heights and spacing from fonts/density.
 * SSD1306 initialization sequence refined for more stable startup.
 * Multiple image assets replaced by symbol-font rendering.
 * Many layout improvements related to density, font scaling and icon scaling
 * Updated folder name capitalization for newer style

Documentation/ideas.md

@@ -87,7 +87,6 @@
 - Remove flex_flow from app_container in Gui.cpp
 - Files app: copy/cut/paste actions
 - ElfAppManifest: change name (remove "manifest" as it's confusing), remove icon and title, publish snapshot SDK on CDN
-- `UiScale` implementation for devices like the CYD 2432S032C
 - Bug: CYD 2432S032C screen rotation fails due to touch driver issue
 - Calculator app should show regular text input field on non-touch devices that have a keyboard (Cardputer, T-Lora Pager)
 - Allow for WSAD keys to navigate LVGL (this is extra nice for cardputer, but just handy in general)