[Compatibility] add `ClickHouseConnection(string connectionString)` constructor

[MaceWindu]

While connection constructor with signature .ctor(string connectionName) is not a part of ADO.NET contract, it is a common thing for provider to have it (I actually don't know any mature provider without such constructor).

This is quite important for integration with libraries (e.g. ORM) that use dynamic provider instantiation using reflection as they could expect such constructor.

[MaceWindu]

Released in 2.2.10