Show panic information in handle_vm_panic

[webmaster128]

Right now, if there is a panic in cosmwasm-vm or libwasmvm, the output looks like this:

Panic in nice_try:
Any { .. }
This indicates a panic in during the operations of libwasmvm/cosmwasm-vm.
Such panics must not happen and are considered bugs. If you see this in any real-world or
close-to-real-world usage of wasmvm, please consider filing a security report,
no matter if it can be abused or not:
(https://github.com/CosmWasm/advisories/blob/main/SECURITY.md#reporting-a-vulnerability).
Thank you for your help keeping CosmWasm safe and secure 💚

where Any { .. } is all we get as the panic information. Not very helpful if things go wrong on a user's machine.

According to the discussion here, there is ways to get the painc string by downcasting.