Reorganize NFT transactions and scripts

[joshuahannan]

Description

• Renames tests to end with _test.cdc
• Reorganize scripts into folders within the transactions/ directory and keep scripts that are purely for tests in the tests/ directory
• Fix a few metadata tests

I'm planning on going through the docs site and cadence-lang.org to make sure all the links to these moved transactions and scripts are fixed

I mostly want to know if we think it is a bad idea to change all these paths since it might break links or dependencies in the ecosystem that link to these scripts. It would be nice to standardize them though so we can have a unified structure among all our repos

[joshuahannan]

I only found one link across the onflow/docs repo and cadence-lang.org repo that needed to be updated, so I make a PR for that: onflow/docs#712. It makes me feel better about the other updated links