1. Do not modify the map after loading. Instead, return string views
(guaranteed to be null-terminated) from look up functions and return
the key directly if not found.
2. Use an `unorded_map` instead of `map` where available (C++20).
Saves a bit of RAM (~50 KiB) and improves lookup performance.
Makes `CelSprite` unowned and adds a new `OwnedCelSprite` class for
owned sprites.
This clarifies ownership and makes the code cleaner in a number of
places.
Additionally, because the `CelSprite` class is now tiny (1 less
pointer), we can pass it by-value instead of by-reference, removing a
pointer indirection in the rendering functions.
1. Increase line height for CJK labels (10->18) to prevent overlap.
2. Increase label width in the right column by 1px (67->68), allowing 3 fullwidth characters to fit on one line.
3. Adjust Base/Now/Gold attribute header positions for CJK.
4. Fix field label/value alignment.