Support TN12 and Covenants++

[smartgoo]

Until covenants++ are merged into rusty-kaspa master branch, this will most likely require a corresponding covpp branch in this repository. Which uses rusty-kaspa covpp branch as the dependency for all RK crates.

Waiting for (relative) cov++ stability in rusty-kaspa prior to doing this.

TODOs as part of this (incomplete):

• Add tn12 branch based on rusty-kaspa covpp branch
• Add all opcodes introduced by cov++ to PyOpcodes enum
• Add forced recipient covenant example in ./examples
• Add vault covenant example in ./examples
• Add token covenant example in ./examples
• Once rusty-kaspa PR 885 is merged, update bindings and examples to use new Covenant Genesis API
• Update CHANGELOG
• Add pages dedicated to Covenants to Docs site

Once rusty-kaspa merges into master, can be moved to main branch here.

[smartgoo]

This is partially complete in branch tn12 of this repository. Which can be used to build the package from source, connect to tn12, and build covenants.

The covenant related Python API will change as the underlying rusty-kaspa covenant API changes.