bound asset metadata strings

[gregdhill]

Use BoundedVec for name and symbol in AssetMetadata so we can derive MaxEncodedLen and remove without_storage_info on the pallet.

[codecov]

Codecov Report

Merging #949 (5e2183a) into master (7582d37) will increase coverage by 0.03%.
Report is 2 commits behind head on master.
The diff coverage is 96.96%.

@@            Coverage Diff             @@
##           master     #949      +/-   ##
==========================================
+ Coverage   78.40%   78.44%   +0.03%     
==========================================
  Files         105      105              
  Lines       10782    10796      +14     
==========================================
+ Hits         8454     8469      +15     
+ Misses       2328     2327       -1     

Files Changed	Coverage Δ
asset-registry/src/impls.rs	52.11% <0.00%> (+0.72%)	⬆️
asset-registry/src/lib.rs	89.53% <ø> (ø)
asset-registry/src/mock/para.rs	70.73% <ø> (ø)
traits/src/asset_registry.rs	100.00% <ø> (ø)
asset-registry/src/mock/mod.rs	78.57% <100.00%> (ø)
asset-registry/src/tests.rs	98.00% <100.00%> (+0.08%)	⬆️

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