Add NFT serialization

[sisyphusSmiling]

Closes: #17
Related: #15
Stacked on #19

Description

This PR introduces a Cadence test framework covering new serialization functionality. Serialization is used on bridging a Cadence-native NFT to EVM, serializing its metadata in conformance with widely used metadata standards (OpenSea's metadata format), and committing the returned data URL JSON string as the tokenURI value in the target ERC721. The same approach is taken to retrieve contract-level metadata, committing the data URL as the contractURI value. In both cases, project-specified URIs defined in CrossVMNFT.EVMBridgedMetadata views are checked first, and serialization is leveraged as a fallback in the event projects did not specify token- or contract-level URIs.

Source contracts are treated as ground truth for NFT metadata, so bridging from native VMs to non-native VMs results in a recommitment of URI values. This means that if metadata will be "synced" to the non-native contract upon bridging between VMs based on state at the time of bridging.

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For contributor use:

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the standards mentioned here.
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov-commenter]

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[nvdtf]

LGTM!