more functionality for dict serialization

[antonydellavecchia]

Adds more functionality for serializing dicts.

Specific use case for when the values are the same type and all share the same parameters

[codecov]

Codecov Report

Merging #3516 (f809352) into master (5acd5c5) will decrease coverage by 0.07%.
Report is 13 commits behind head on master.
The diff coverage is 96.42%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3516      +/-   ##
==========================================
- Coverage   82.18%   82.11%   -0.07%     
==========================================
  Files         563      566       +3     
  Lines       75862    76165     +303     
==========================================
+ Hits        62345    62545     +200     
- Misses      13517    13620     +103     

Files	Coverage Δ
src/Serialization/containers.jl	94.61% <96.42%> (+0.14%)	⬆️

... and 22 files with indirect coverage changes