#2861 generate: STRATA_VRAM_RESERVE_MIB, a VRAM reserve per part

Descripción

--vram-reserve-mib sizes the first card and --vram-reserve-later-mib puts one number on every later card.  A layer split on cards of different sizes wants one reserve per card instead.  STRATA_VRAM_RESERVE_MIB (and its alias STRATA_GLM_RESERVE_MB) takes a comma list: entry 0 is the first card and replaces --vram-reserve-mib, entry i is the i-th later card; a shorter list reuses its last number and extra numbers are ignored.  Values are MiB.

stage_room() now prefers the list's entry for its part ordinal in the split search, the stage sizing, the drafter, and the LOW free-VRAM warning, whose fix line names the list entry when the list is active.  A start line prints the reserve each part will use.

Unset, the two flags decide exactly as before and the run is byte-identical. Ported from the Maya checkout's STRATA_GLM_RESERVE_MB (Glm5Model::pool_reserve).

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