[costs] Represent cost functions for Clarity 2 functions

[gregorycoppola]

Is your feature request related to a problem? Please describe.
We don't have a way to represent costs for Clarity 2 functions. This means that existing cost functions have to be arbitrarily reused.

Additional context
I think the reason this is non-trivial is because it would be a consensus breaking change?

#2691 (comment)

[kantai]

Thanks for opening @gregorycoppola -- yeah, I think this is just a little subtle to implement without altering the consensus before the epoch switch.

I think that in order to implement this, we would need to:

1. Add a new default cost contract instantiation at the "epoch-switch" boundary.
2. Change the CostTracker implementation to use that default cost contract for Clarity2 functions.
3. Change the CostTracker implementation so that it only matches new cost functions based on the active Clarity version (not the contract version)

[jcnelson]

Closing in favor of #3115. Most of this work is done already in 2.05.

[blockstack-devops]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.