policy-evaluator: evaluate a Rego policy converted to Wasm

[flavio]

• Turn https://github.com/flavio/burrego into a crate
• Allow the creation of a policy evaluator that can evaluate Rego code

Part of #14

[ereslibre]

https://github.com/wapc/wasmtime-provider/pull/10 is part of this work. The burrego crate was depending on wasmtime 0.28.0 and since we depend on that crate too but on version 0.24.0 -- and given it links to the system, only one crate version can exist in the dependency graph. Thus, as part of this work, we had to bump the wasmtime-provider of the wapc project to 0.28.0 too, and so the dependency graph is solved for this project.