dat: sample each case once, show every piece of each archive, type elided data

[ribbanya]

Samples are now chosen across every archive by a samples pick step: for each type and union variant, the fewest instances that together show every case its fields take anywhere in the game (pointers null, relocated, unrelocated or -1; float and integer classes; bitfields; nonzero padding), preferring instances the walk found clean. Each archive's choice is rewritten only when it changes. Sample-mode C goes from 12,130 samples (245k lines) to 347 (13k lines), and every unit is in objdiff, samples or not. MELEE_DAT_SAMPLES_ALL still samples everything.

Elided data is declared as the type the walk reached it as, spelled as the pointers to it spell it (Mtx, HSD_DisplayList[n], u16[n]), instead of UNK_T. MtxPtr, Mtx44Ptr and ROMtxPtr are redeclared with DAT_TYPE in dat_macros.h for the DWARF build, which uses aurora's SDK headers.

Every piece of each archive outside the samples is now its own symbol in the target, and the base infers each piece the walk explains on its own, instead of only public symbols and data the samples point to, each with everything it reaches. So what's inferred no longer depends on what's sampled: units without samples show all their data, and 106 units are complete in both modes. Bytes a pointer says are bytes (texels, strings, keyframes) and command scripts up to their end command count as explained.

A union member condition that can't be evaluated now stops the search instead of falling through to a later member, so ftData_Item uses DAT_IF(1) as its catch-all.