Network parameter validation on proposals

[davidsiska-vega]

We can validate parameter ranges at proposal submission (and I believe we do).

However, relation to anything dynamic, especially other parameter values must only happen at enactment time:

• if, at enactment time validation against other dynamic values (other parameter values) passes, proposal goes ahead
• else proposal fails (and if this is part of a batch then only this part of the batch fails, the rest remains scheduled as when it passed voting).

We need to:

• update spec to make this clear
• add an AC

[witgaw]

#2362