Implemented custom SQL DB registration

[zaleslaw]

This pull request introduces several enhancements to the dataframe-jdbc module, primarily focusing on adding support for custom database types (DbType) in various methods. Additionally, it includes a minor change to make the H2 class extensible.

Also, this PR in the client application is based on 0.15-dev built on this branch

Enhancements to database type support:

• dataframe-jdbc/src/main/kotlin/org/jetbrains/kotlinx/dataframe/io/readJdbc.kt:
  • Added optional dbType parameter to multiple methods, allowing custom database type objects to be passed. This parameter defaults to null and, if not provided, the database type is determined from the connection.

Minor changes:

• dataframe-jdbc/src/main/kotlin/org/jetbrains/kotlinx/dataframe/io/db/H2.kt:
  • Changed H2 class to be open, allowing it to be extended.

For finalization, it requires

• [ ] the update of readFromSQL.md
• [ ] Linter check