[NFT-Staking] Attribute namespace support

[DidacSF]

Description

This PR adds limited AttributeNamespace support similar to what https://github.com/paritytech/substrate/blob/polkadot-v0.9.42/frame/nfts/src/types.rs#L326 accomplishes.

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: 88.88% and no project coverage change.

Comparison is base (3bffff4) 74.98% compared to head (560a3eb) 74.99%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #338   +/-   ##
========================================
  Coverage    74.98%   74.99%           
========================================
  Files           33       33           
  Lines         3422     3427    +5     
========================================
+ Hits          2566     2570    +4     
- Misses         856      857    +1     

Files Changed	Coverage Δ
pallets/ajuna-nft-staking/benchmarking/src/lib.rs	0.00% <ø> (ø)
pallets/ajuna-nft-staking/src/contracts.rs	93.10% <88.88%> (-2.73%)	⬇️

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