feat(cubejs-server-core): add dbType to dataSources

[wolfeeeg]

Check List

• Tests has been run in packages where changes made if available
• Linter has been run for changed code
• Tests for the changes have been added if not covered yet
• Docs have been added / updated if required

Issue Reference this PR resolves

[For example #12]

Description of Changes Made (if issue reference is not provided)

[Description goes here]

[codecov]

Codecov Report

Base: 41.60% // Head: 41.61% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (2ecdcb4) compared to base (7cb2eef).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 2ecdcb4 differs from pull request most recent head d6a0715. Consider uploading reports for the commit d6a0715 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6089   +/-   ##
=======================================
  Coverage   41.60%   41.61%           
=======================================
  Files         152      152           
  Lines       20092    20093    +1     
  Branches     5238     5238           
=======================================
+ Hits         8360     8361    +1     
  Misses      11422    11422           
  Partials      310      310           

Flag	Coverage Δ
cube-backend	41.61% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ackages/cubejs-server-core/src/core/CompilerApi.js	85.00% <100.00%> (+0.12%)	⬆️
...es/cubejs-schema-compiler/src/adapter/BaseQuery.js	70.77% <0.00%> (ø)

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