ENH: change to_sql default from Text to UnicodeText
#### Is your feature request related to a problem?

Yes. Databases that differentiate between Unicode and SBCS columns (notably Microsoft SQL Server `nvarchar` vs. `varchar`) can fail simple round-trips when using `to_sql` to write columns with Unicode strings.

#### Describe the solution you'd like

Change the default column `dtype` from `Text` ...

https://github.com/pandas-dev/pandas/blob/a9cb64ad105f8f7051f9d77b66e1bfe7c09d386f/pandas/io/sql.py#L1080

... to `UnicodeText`.

#### API breaking implications

None that I can see.

#### Describe alternatives you've considered

An alternative would be to modify the behaviour of `Text` in SQLAlchemy's mssql dialect, but SQLA already has `UnicodeText` and it solves the problem.

#### Additional context

```python
import pandas as pd
import sqlalchemy as sa

engine = sa.create_engine("mssql+pyodbc://@mssqlLocal")

df = pd.DataFrame(
    [("English", "CHEERS!"), ("Greek", "ΟΠΑ!")], columns=["language", "toast"]
)
df.to_sql("pd_test", engine, index=False, if_exists="replace")
print(pd.read_sql_query("SELECT * FROM pd_test", engine))
"""console output:
  language    toast
0  English  CHEERS!
1    Greek     ???!
"""
```
