fix(schema-compiler): Allow calling cube functions in yaml python blocks

[KSDaemon]

Previously it was impossible to call sql() or other functions of other cubes.
Now it's fixed!

So you can do for example this in yaml models:

cubes:
  - name: simple_orders
    sql: >
      SELECT 1 AS id, 100 AS amount, 'new' status, now() AS created_at

...

  - name: simple_orders_sql_ext

    sql: >
      SELECT * FROM {simple_orders.sql()}                <<<<<< this <<<<<<
      WHERE status = 'processed'

....

Fixes #7484

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.46%. Comparing base (0a8cf07) to head (fff648e).
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #9473       +/-   ##
===========================================
+ Coverage   48.16%   58.46%   +10.29%     
===========================================
  Files         171      167        -4     
  Lines       21454    14927     -6527     
  Branches     3724     2955      -769     
===========================================
- Hits        10334     8727     -1607     
+ Misses      10692     5854     -4838     
+ Partials      428      346       -82     

Flag	Coverage Δ
cube-backend	58.46% <100.00%> (+10.29%)	⬆️

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