MVP - Basic ACL example and runtime

[jakehemmerle]

These tracking tickets somewhat depend on each other so will be written in parallel:

• [x] #9

MVP will be the most barebones constraint possible:

• [x] a Wasm-executable following a basic ABI:
  • _start function that takes a single string as input and returns the result<_, errno> type. See the component model types here.
• [x] able to parse a single, basic, EVM transaction
• [x] an ACL constraint
  • if the constraints are not satisfied, return errno
  • if they are satisfied, return _
• [x] #14

To be clear, outside of the MVP scope is:

• most of #3

• 1

• linking at runtime
• custom runtime APIs (no WASI or non-standard WITs; _start is pure)
• additional inputs at start (eg stateful data like tokens_per_day or merkle branches)
• return values other than _ or errno (eg delta(s) of some stateful input)

I could use some help with

• [x] https://github.com/entropyxyz/entropy-core/issues/318
• [x] https://github.com/entropyxyz/entropy-core/issues/319
• [x] https://github.com/entropyxyz/entropy-js/issues/145

After those two, we can start integrating the wasmi interpreter into the threshold server too (and the SDK!), but this should wait a bit, since I might want to tightly integrate subxt for reliability when we get to dynamic linking.

[jakehemmerle]

ABI is not as defined above, but is similar. will be doc'd elsewhere