BIP-0158: regenerate test vectors for fp=19, new reg filter, no ext filter

In this commit, we simplify the code that generates the test vectors to
only generate filters for a target fp of 19, and also only for the
regular filter, as it's the only filter type currently defined.

The test vectors have also been updated to include the previous output
scripts for all input within a block as these are now required to
construct the regular filter.

Finally, the generation code has been updated to properly fetch the
previous input scripts to the generation code can verify the filter it
generates manually against the end server.

Author: Roasbeef