fx_importer_tosa: `BertModule` e2e test times out

[justin-ngo-arm]

BertModule e2e test timed out because of TOSA's TosaLayerwiseConstantFoldPass. This is because it takes too long for this pass to go through and fold all constant layerwise ops in the BertModule end-to-end. One potential fix is to apply this pass with a model size limit; if a model is too big, we will skip applying this pass to avoid the time-consuming folds.