[FEATURE] Pass default VARCHAR size in the connection string instead of hard coding 65536 in the code

## Is your feature request related to a problem? Please describe.

Some systems like Informatica doesn't support 65536 characters in string coumns. So this driver is not useful as it is

## Describe the solution you'd like

If I pass varchar size in connection string (ex. 4000), it would be useful

## Describe alternatives you've considered

May be in the schema tables?

## Additional context

Start by locating the code that hard-codes VARCHAR size 65536 and the connection-string parsing entry point. Trace how the default size is applied to generated schema or query metadata, then define and verify the connection-string option so a value such as 4000 replaces the hard-coded default.

Written by the indexing model from the issue text.