Draft: Add a new consensus method to find bwweightscale correctly.

Our original code for parsing bwweightscale out of our list of parameters pre-dated us having the dirvote_get_intermediate_param_value() function... and it was buggy. Specifically, it would reject any " ... bwweightscale=X ..." value where there were additional unconverted characters after the X, and use the default value.

We haven't run into this yet because we've never voted for bwweightscale to be anything besides the default 10000.

This requires a new consensus method because it is a change in how consensuses are computed.

Fixes #19011 (closed); bugfix on 0.2.2.10-alpha.