[FEATURE] New datasource - machine learning (ML)

[Yury-Fridlyand]

Is your feature request related to a problem?

SQL plugin depends on ML plugin which depends on ....

What solution would you like?

Create new datasource: ML

1. It will use ML to obtain data (the same happens now)
2. It will provide few unique functions (now those functions exist in the common scope - kmeans, knn, ad, ml, etc)
3. It will be pluggable, so
   3.1. We could be able to deactivate it in case of dependency conflict or any other compilation errors.
   3.2. Probably, the end user would be able to opt-in/out this feature too in the SQL plugin.

What alternatives have you considered?

N/A

Do you have any additional context?

1. Common compilation errors due to ML dependency
2. Doctests are disabled for ML

The goal

To avoid having a strict dependency on ML plugin. Make this dependency loose and/or optional.

[Yury-Fridlyand]

Related to #811