YT: https://youtrack.raccoongang.com/issue/EDX_BLND_CLI-87
- V2 libraries are available for selection in the Random Block edit modal;
- selected V2 library blocks are copied to the modulestore and saved as children of the Random Block;
- V2 library version validation works the same as for the V1 libraries (with possibility to update block with the latest version);
- filtering by problem type can't be done for V2 the same as for V1 because the v2 library problems are not divided by types;
- the problem type field is hidden for v2 libraries in the edit mode;
- unit tests added/updated.
dcf1cc14b6