Move realDatabaseName out of the SqlServerConnection state

[morozov]

Currently, the "real" name of the source database is detected right after connecting to the database at the connection level:

debezium/debezium-connector-sqlserver/src/main/java/io/debezium/connector/sqlserver/SqlServerConnection.java

Lines 116 to 120 in e1cf58f

	public SqlServerConnection(Configuration config, Clock clock, SourceTimestampMode sourceTimestampMode, SqlServerValueConverters valueConverters,
	Supplier<ClassLoader> classLoaderSupplier) {
	super(config, FACTORY, classLoaderSupplier);
	lsnToInstantCache = new BoundedConcurrentHashMap<>(100);
	realDatabaseName = retrieveRealDatabaseName();

In order to make the connection reusable across multiple databases (#10), we need to:

1. Detect the "real" name of all databases the task is working with.
2. Make the real name available to all components that use it right now.

The most natural place for that seems to be the SqlServerTaskPartition and its Provider being introduced as part of #15.

Acceptance criteria:

1. Add a dependency on SqlServerConnection to SqlServerPartitionTask.Provider.
2. While initializing each task partition, execute a query like:

   SELECT name FROM sys.databases WHERE name = ?;

   It will return the database name in its actual case (e.g. mAsTeR → master).
3. If the query above doesn't return one and only one row, JDBC will throw an exception which the code should catch and log as a warning. No reason to fail the task.
4. Initialize each SqlServerTaskPartition with a real database name instead of the configured one.
5. Remove the current logic from the connection class.