feat: map TFLite indices computed at run time

[asteinh]

• GATHER, GATHER_ND, EMBEDDING_LOOKUP and DYNAMIC_UPDATE_SLICE take their indices or start positions from an int32 model input or an ARG_MAX/ARG_MIN output, besides constants.
• A DYNAMIC_UPDATE_SLICE with run-time starts runs in TFLite's axis order, so the starts are used as they are.
• Refused by name: an index tensor feeding an operand other than indices, run-time indices computed by any operator other than ARG_MAX/ARG_MIN, and int64 run-time indices.
• Ten new corpus cases (gather, gather_nd, embedding_lookup, ArgMax feeding gather, and dynamic_update_slice with starts that reach past both ends), int8 and float32, match TFLite Micro byte for byte, untiled and at the 256-byte budget.