Decompress image assets found in the stage files as PNGs

[Xeeynamo]

Instead of outputting a D_80123456.dec from an extracted compressed asset, now a PNG is written from the decompressed data from the specified YAML entry. The asset tool will synchronize with splat to retrieve the symbol names for graphics and palettes. The new splat extension cmpgfx will also be able to detect unused graphics by failing with a hint on how to tweak the YAML. That way I found some unused placeholders under the name stage_placeholder and some kind of beta graphics from the prologue stage.

[github-actions[bot]]

STCEN hd

data 84.33% (-12.60%)

[github-actions[bot]]

STDRE us

data 97.40% (-0.05%)

STNZ0 us

data 99.99% (+0.57%)

STST0 us

data 95.78% (+1.72%)

[github-actions[bot]]

STCEN hd

data 84.33% (-12.60%)

[github-actions[bot]]

STDRE us

data 97.40% (-0.05%)

STNZ0 us

data 99.99% (+0.57%)

STST0 us

data 95.78% (+1.72%)