[PLAT-763], [PLAT-764] Refactor NFT ownership with immutable attributes

[cowboy-bebug]

Description

Re: PLAT-763 & PLAT-764

Main changes:

• update the ownership of an avatar like below:
  • player owns avatar initially, and on store_as_nft:
    • pallet account owns the avatar in pallet-ajuna-awesome-avatars
    • player owns the NFT of the avatar in pallet-nfts
      • at a later offloading stage, the ownership will be transferred to pallet-ajuna-nft-transfer's pallet account
• disable PalletFeature::Attributes to prevent attribute mutation through the pallet-nfts extrinsics
• Remove NextItemId and use AvatarId (H256) as the ItemId
  • (to ensure unique avatars are stored under a collection)

Type of changes

• build: Changes that affect the build system or external dependencies (eg, Cargo, Docker)
• ci: Changes to CI configuration
• docs: Changes to documentation only
• feat: Changes to add a new feature
• fix: Changes to fix a bug
• refactor: Changes that do not alter functionality
• style: Changes to format the code
• test: Changes to add missing tests or correct existing tests

Checklist

• Tests for the changes have been added
• Necessary documentation is added (if appropriate)
• Formatted with cargo fmt --all
• Linted with cargo clippy --all-features --all-targets
• Tested with cargo test --workspace --all-features --all-targets

[codecov]

Codecov Report

Patch coverage: 75.86% and project coverage change: -0.15 ⚠️

Comparison is base (6f5dcbd) 77.70% compared to head (381db68) 77.56%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #246      +/-   ##
===========================================
- Coverage    77.70%   77.56%   -0.15%     
===========================================
  Files           17       17              
  Lines         1144     1141       -3     
===========================================
- Hits           889      885       -4     
- Misses         255      256       +1     

Impacted Files	Coverage Δ
pallets/ajuna-awesome-avatars/src/migration/v4.rs	0.00% <0.00%> (ø)
pallets/ajuna-nft-transfer/src/traits.rs	100.00% <ø> (ø)
pallets/ajuna-nft-transfer/src/lib.rs	72.34% <78.57%> (+2.98%)	⬆️
pallets/ajuna-awesome-avatars/src/lib.rs	89.04% <100.00%> (+0.29%)	⬆️
...lets/ajuna-awesome-avatars/src/types/avatar/nft.rs	100.00% <100.00%> (ø)

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