When we moved WT_CURSTD_IGNORE_TOMBSTONE from being a session flag to a cursor flag, we broke wt dump. wt dump uses a dump cursor which delegates calls to the cursor API to a "child" cursor. We need to set the flag on the child cursor for this to work.

We also modified the check in __wt_txn_read such that we will read the on-disk value's stop time pair even with WT_CURSTD_IGNORE_TOMBSTONE enabled if it is globally visible. This isn't useful for wt dump so we need an exception here.