Re-export Slow Update tree dependencies via aztec.js

[rahul-kothari]

Currently e2e test imports @aztec/kv-store and @aztec/merkle-tree. But users shouldn't be using these packages. So:

1. Re-export required methods via aztec.js
2. Add a comment in e2e package.json - telling devs not to import additional packages there (since e2e should be a relfection of what external devs do)
3. Add a linter rule in e2e so we don't do this again.

[rahul-kothari]

closed in #4483