[SCHEMA] Create macro to render fields within objects

[tsalo]

Closes #841.

Basically, we can move sub-object definitions into the actual object definitions now that we have a function to render sub-objects directly.

Here's what the new Genetics metadata sub-object table looks like:

I can adopt any kind of notation for the key name column. Maybe Genetics[Dataset]? [Genetics]Dataset?

[codecov]

Codecov Report

Merging #1097 (2296d0b) into master (a4a03dd) will increase coverage by 0.35%.
The diff coverage is 68.57%.

@@            Coverage Diff             @@
##           master    #1097      +/-   ##
==========================================
+ Coverage   70.75%   71.11%   +0.35%     
==========================================
  Files           9        9              
  Lines         937      952      +15     
==========================================
+ Hits          663      677      +14     
- Misses        274      275       +1     

Impacted Files	Coverage Δ
tools/schemacode/schemacode/render.py	92.83% <68.57%> (-3.22%)	⬇️
tools/schemacode/schemacode/_version.py	38.90% <0.00%> (+2.59%)	⬆️

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[sappelhoff]

lgtm, +1 to merge after a rebase and observing the "review time"

[Remi-Gau]

That'd be REALLY nice to have in. Thanks @tsalo

[tsalo]

If no one raises an issue with this one I'll merge it tomorrow.