generateRandom() does not support generating random Date32 value:

```
SELECT *
FROM generateRandom('Date32 Date32', NULL, 10, 2)
LIMIT 10

Received exception from server (version 21.11.5):
Code: 48. DB::Exception: Received from localhost:9000. DB::Exception: The 'GenerateRandom' is not implemented for type Date32: While executing GenerateRandom. (NOT_IMPLEMENTED)
```

{
public:
    GenerateSource(UInt64 block_size_, UInt64 max_array_length_, UInt64 max_string_length_, UInt64 random_seed_, Block block_header_, ContextPtr context_)
        : SourceWithProgress(Nested::flatten(prepareBlockToFill(block_header_)))
        , block_size(block_size_), max_array_length(max_array_length_), max_string_length(max_string_length_)
        , block_to_fill(std::move(block_header_)), rng(random_seed_), context(context_) {}
    String getName() const override { return "GenerateRandom"; }