feat(schema-compiler,api-gateway): Nested folders support

[KSDaemon]

This PR brings nested folder support into views.
So now you can define this:

  - name: test_view
    folders:
      - name: folder1
        includes:
          - users_city
          - name: inner folder 2
            includes:
              - renamed_orders_status
          - name: inner folder 3
            includes: "*"

/meta endpoint was extended with additional cube property nestedFolders, which holds the recursive nested folders structure. Original folders property is kept untouched for backward compatibility.

Additional env flag CUBEJS_NESTED_FOLDERS_DELIMITER was introduced. It controls how to form the flatten folders property in meta data. If it is not set - all nested folders members will be merged to the root folder members. If it is set to some string (e.g. "/"), then nested folders are bubbled to the root level with their names being constructed as root folder/nested folder/deep nested simulating a nested structure for those APIs (probably some BI tools) that don't support nested folders out of the box.

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

[ovr]

Please regenerate /rust/cubeclient client. Thanks

[codecov]

Codecov Report

Attention: Patch coverage is 69.23077% with 4 lines in your changes missing coverage. Please review.

Project coverage is 84.22%. Comparing base (340f97e) to head (2eddf29).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...ubeclient/src/models/v1_cube_meta_nested_folder.rs	0.00%	3 Missing ⚠️
rust/cubesql/cubeclient/src/models/v1_cube_meta.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9659   +/-   ##
=======================================
  Coverage   84.22%   84.22%           
=======================================
  Files         231      232    +1     
  Lines       85494    85507   +13     
=======================================
+ Hits        72005    72018   +13     
  Misses      13489    13489           

Flag	Coverage Δ
cubesql	84.22% <69.23%> (+<0.01%)	⬆️

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