V210.hpp: add fill_colorbars, fill_ire_ramp, fill_black, fill_white.
Shared fill_solid helper stamps the first line across all rows via
memcpy. Generic write_palette_line template handles both SMPTE and
IRE bar palettes. fill_frame kept as a backward-compat alias.
testpattern/main.cpp: read "pattern" from node config and dispatch
to the appropriate fill function (bars/ire/black/white).
build_graph: pass {"pattern","bars"} to testpattern node params.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
itten