remove nft-utils and move the code into sov-nft-module and demo-rollup

[dubbelosix]

Description

Refactoring the location and structure of the sov-nft-module interaction code.

Context:

Previously, the code to interact with the sov-nft-module was located in a separate top-level project named utils/nft-utils. This arrangement was chosen because this code depended on the Runtime for encoding the enum variant of calls and transaction creation.

Problem:

Having nft-utils at the top level creates a compilation issue if someone decides to remove the sov-nft-module.

Proposed Solution:

This PR proposes a better organized solution:

• Move the utility functions that construct the enum variant into utils.rs inside the sov-nft-module.
• Introduce a new binary at demo-rollup/src/bin/sov-nft-script.rs. This binary will leverage the utilities from sov-nft-module and handle transaction construction.
• The original nft-utils has been completely removed.

[codecov]

Codecov Report

Merging #992 (3d495d9) into nightly (1a73dae) will increase coverage by 0.7%.
The diff coverage is 0.0%.

Files	Coverage Δ
...module-implementations/sov-nft-module/src/utils.rs	18.9% <0.0%> (-81.1%)	⬇️

... and 3 files with indirect coverage changes