Mesh 1865/asset metadata improvements

[HenriqueNogara]

Adds two extrinsics: remove_local_metadata_keyand remove_metadata_value.

changelog

new features

• remove_local_metadata_key extrinsic;
• remove_metadata_value extrinsic;

modified API

• Adds two error variants: AssetMetadataKeyBelongsToNFTCollection, AssetMetadataValueIsEmpty
• Adds two events: MetadataValueDeleted, LocalMetadatakeyDeleted

modified logic

• base_set_asset_metadata_details no longer allows locking a key with empty value.

[codecov[bot]]

Codecov Report

Merging #1398 (b834aa9) into develop (2c90c72) will increase coverage by 0.02%. The diff coverage is 48.06%.

@@             Coverage Diff             @@
##           develop    #1398      +/-   ##
===========================================
+ Coverage    44.20%   44.23%   +0.02%     
===========================================
  Files          146      146              
  Lines        31124    31252     +128     
===========================================
+ Hits         13758    13823      +65     
- Misses       17366    17429      +63     

Impacted Files	Coverage Δ
pallets/common/src/traits/asset.rs	0.00% <0.00%> (ø)
pallets/common/src/traits/nft.rs	0.00% <ø> (ø)
pallets/runtime/common/src/runtime.rs	1.86% <ø> (ø)
pallets/weights/src/pallet_asset.rs	3.33% <0.00%> (-0.24%)	:arrow_down:
pallets/asset/src/lib.rs	60.92% <51.88%> (-0.47%)	:arrow_down:
pallets/nft/src/lib.rs	63.25% <100.00%> (+0.84%)	:arrow_up:
primitives/src/asset_identifier.rs	98.34% <0.00%> (+0.41%)	:arrow_up:
pallets/identity/src/claims.rs	90.80% <0.00%> (+0.57%)	:arrow_up: