Test av_tdrdi_alloc with 1 and 3 displays, and the inline
av_tdrdi_get_display accessor. Verifies that the returned
pointer matches entries_offset + idx * entry_size, tests
write/read-back of display width exponent/mantissa and view ID
fields, and OOM paths via av_max_alloc.
Coverage for libavutil/tdrdi.c: 0.00% -> 100.00%