konami/mystwarr_v.cpp, k053246_k053247_k055673.cpp: improve sprite blending (#13328)

* mystwarr & metamrph & dadandrn sprite callbacks:
mark sprites with their attribute bits for blending

* reverse sprite blending

* minor k053247_device::zdrawgfxzoom32GP cleanup:
-move variable declarations closer to use
-use appropriate variable types
-mark applicable variables as const
-move "cull off-screen objects" early out check earlier in function
-move back "dst_" vars under appropriate comment
-further reduce reuse of "eax" variable
-use cliprect directly inside function
-rename various "eax" variables
-simplify switch-case to if statement

Author: FredYeye