Add NonFungible types; Add `BalanceOf` to the NFT pallet; Add `asset_type` checks

[HenriqueNogara]

Adresses the comments in #1389

changelog

modified API

• Adds the following error variants to the asset pallet:
  • UnexpectedNonFungibleToken, IncompatibleAssetTypeUpdate;
• Adds the following error variants to the nft pallet:
  • InvalidNFTTransferFrozenAsset;
• Adds NonFungible(NonFungibleType) to AssetType:
• Adds BalanceOf storage in the NFT pallet;

modified logic

• validate_nft_transfer checks if the asset is frozen;
• base_update_asset_type fails updating a fungible asset to a non-fungible one, and the other way around.
• unsafe_transfer, _mint, base_make_divisible, and base_redeem return an error for non-fungible tokens.

[codecov[bot]]

Codecov Report

Merging #1399 (44e9a4d) into MESH-1890/add-nft-pallet (8543fd5) will decrease coverage by 0.05%. The diff coverage is 75.00%.

@@                     Coverage Diff                      @@
##           MESH-1890/add-nft-pallet    #1399      +/-   ##
============================================================
- Coverage                     43.69%   43.65%   -0.05%     
============================================================
  Files                           145      145              
  Lines                         31175    31218      +43     
============================================================
+ Hits                          13623    13628       +5     
- Misses                        17552    17590      +38     

Impacted Files	Coverage Δ
primitives/src/nft.rs	77.35% <ø> (-1.22%)	:arrow_down:
pallets/asset/src/lib.rs	60.32% <67.85%> (+<0.01%)	:arrow_up:
pallets/nft/src/lib.rs	62.41% <74.07%> (+0.04%)	:arrow_up:
primitives/src/asset.rs	46.93% <91.66%> (+14.50%)	:arrow_up:
pallets/settlement/src/lib.rs	49.09% <100.00%> (-1.29%)	:arrow_down:
primitives/src/asset_identifier.rs	97.92% <0.00%> (-0.42%)	:arrow_down:
pallets/balances/src/lib.rs	57.10% <0.00%> (-0.14%)	:arrow_down: