refactor: investigate pre-epoch 2.1 ASTRules vs post-epoch 2.1 ASTRules

[jferrant]

There currently are ASTRules::Typical and ASTRules::PreCheckSize.
Basically, PrecheckSize rules are a further constraint atop the Typical rules -- i.e. pre-check the size of the expression stack depth when parsing (i.e. before type-checking). PreCheckSize is required for POST epoch 2.1 rules. However, it is possible that PRE epoch 2.1 rules could also include these PreCheckSize and consensus not break. If so, then we drop ASTRules altogether and make the PrecheckSize code paths the only code paths.

[jferrant]

Ran a replay with a minimum change to check if it is viable. unfortuantely not as there are many pre epoch 2.1 blocks that seem to violate the prechecksize rules. EDIT: this was a mistake int he original branch. Rerunning with corrected branch passes replay. Reopening.