DNM: feat(x/ecocredit): start migrating ORM tables to declarative protobuf

[aaronc]

Description

DO NOT MERGE

I would like to start at least expressing the ORM schema in protobuf even if we can't quite generate the ORM from protobuf yet. This PR proposes an approach for that.

I've noticed some issues with our current schema - for instance CreditType embedded in ClassInfo is denormalized and we really want to avoid that. So I think if we at least start describing a relational schema declaratively (whcih we can do in protobuf) we'll be able to evaluate the design better.

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[codecov]

Codecov Report

Merging #651 (7760038) into master (9c97674) will decrease coverage by 0.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #651      +/-   ##
==========================================
- Coverage   73.70%   73.58%   -0.13%     
==========================================
  Files         104      105       +1     
  Lines       14948    14832     -116     
==========================================
- Hits        11018    10914     -104     
- Misses       3153     3164      +11     
+ Partials      777      754      -23     

Flag	Coverage Δ
experimental-codecov	73.58% <ø> (-0.13%)	⬇️
stable-codecov	65.33% <ø> (-0.15%)	⬇️

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[robert-zaremba]

done in #700