**Describe the bug**
Here's my table:
```sql
CREATE TABLE table2
(
        EventDate Date,
        Id Int32,
        Value Int32
)
Engine = MergeTree()
PARTITION BY toYYYYMM(EventDate)
ORDER BY Id;
```

Modify default value (intentionally wrong):
```
>>> alter table table2 modify column Value default 'some_string';

ALTER TABLE table2
    MODIFY COLUMN `Value` DEFAULT 'some_string'

Ok.

0 rows in set. Elapsed: 0.007 sec. 
```

Now you obviously cannot insert anything to this table, because:
```
>>> insert into table2 (EventDate, Id) values (1234567890, 2)

INSERT INTO table2 (EventDate, Id) VALUES

Received exception from server (version 20.9.3):
Code: 6. DB::Exception: Received from localhost:9000. DB::Exception: Cannot parse string 'some_string' as Int32: syntax error at begin of string. Note: there are toInt32OrZero and toInt32OrNull functions, which returns zero/NULL instead of throwing exception.. 

1 rows in set. Elapsed: 0.002 sec. 
```

**How to reproduce**
* Which ClickHouse server version to use: 20.9.3
* Which interface to use, if matters: I used standard CLI

**Expected behavior**
Currently ClickHouse doesn't check types compability while setting a DEFAULT value for a column. Maybe ClickHouse should validate DEFAULT values for type compability?

else if (command.type == AlterCommand::ADD_COLUMN)
        {
            if (has_column && command.if_not_exists)
                command.ignore = true;
        }
        else if (command.type == AlterCommand::DROP_COLUMN
                || command.type == AlterCommand::COMMENT_COLUMN
                || command.type == AlterCommand::RENAME_COLUMN)
        {
            if (!has_column && command.if_exists)
                command.ignore = true;
        }
    }
    prepared = true;
}
void AlterCommands::validate(const StorageInMemoryMetadata & metadata, const Context & context) const
{
    auto all_columns = metadata.columns;
    
    ASTPtr default_expr_list = std::make_shared<ASTExpressionList>();
    NameSet modified_columns, renamed_columns;
    for (size_t i = 0; i < size(); ++i)
    {
        const auto & command = (*this)[i];
        const auto & column_name = command.column_name;
        if (command.type == AlterCommand::ADD_COLUMN)
        {
            if (all_columns.has(column_name) || all_columns.hasNested(column_name))
            {
                if (!command.if_not_exists)