Add ConstSize wrapper.

[Neopallium]

Adds ConstSize wrapper for const u32 values. This is needed for the size limits for bounded collections like BoundedBTreeMap to be used as extrinsic parameters, since extrinsic parameters need extra traits (Clone, Debug, PartialEq, Eq) and this also applies to the size limit generic type parameter on bounded collections.

[codecov]

Codecov Report

Merging #1530 (321374e) into develop (3ab8456) will increase coverage by 0.10%.
The diff coverage is 0.00%.

❗ Current head 321374e differs from pull request most recent head d03db46. Consider uploading reports for the commit d03db46 to get more accurate results

@@             Coverage Diff             @@
##           develop    #1530      +/-   ##
===========================================
+ Coverage    58.54%   58.65%   +0.10%     
===========================================
  Files          142      142              
  Lines        31992    31885     -107     
===========================================
- Hits         18730    18702      -28     
+ Misses       13262    13183      -79     

Files	Coverage Δ
pallets/common/src/lib.rs	64.61% <0.00%> (-4.24%)	⬇️

... and 6 files with indirect coverage changes