fix(schema-compiler): Collect join hints from subquery join conditions

[mcheshkov]

Check List

• Tests have 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

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

This is necessary to support queries where output references only join subqueries.
Before, when query does have subqeury joins, but does not have any measures/dimensions/... join hints would be empty, and join tree would be null, which is almost okay, but to generate query with join subqueries we need to build join query, so join tree is more-or-less required.

[codecov]

Codecov Report

Attention: Patch coverage is 37.50000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 61.70%. Comparing base (1deddcc) to head (460d5ff).
Report is 31 commits behind head on master.

Files with missing lines	Patch %	Lines
...es/cubejs-schema-compiler/src/adapter/BaseQuery.js	37.50%	5 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (1deddcc) and HEAD (460d5ff). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (1deddcc)	HEAD (460d5ff)
cubesql	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #9554       +/-   ##
===========================================
- Coverage   80.39%   61.70%   -18.70%     
===========================================
  Files         395      174      -221     
  Lines       97932    14439    -83493     
  Branches     2278     2464      +186     
===========================================
- Hits        78731     8909    -69822     
+ Misses      18893     5161    -13732     
- Partials      308      369       +61     

Flag	Coverage Δ
cube-backend	61.69% <37.50%> (+4.35%)	⬆️
cubesql	?

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[KSDaemon]

👍🏻 LGTM!