feat: Tap level SQLAlchemy connector instance shared with Streams

[BuzzCutNorman]

Feature scope

Taps (catalog, state, stream maps, tests, etc.)

Description

Currently an SQL tap will open and hold a session to the source for each stream selected. This means if a tap has 100 streams\tables selected the SQL tap will open 100 session and hold them until the meltano run is finished. It would be nice if SQL taps could utilize a single connector instance and leverage the SQLAlchemy pool of connection it has.

This could be accomplished If an instance of the tap's connector class is initialized and held as a property and that connector property is passed on to SQLStream instances when they are initialized by the discover_streams method. The changes to the SQLTap class might look like this:

class SQLTap(Tap):
    """A specialized Tap for extracting from SQL streams."""

    # Stream class used to initialize new SQL streams from their catalog declarations.
    default_stream_class: type[SQLStream]

    default_connector_class = SQLConnector
    _tap_connector: SQLConnector = None

    ... comments and code removed to show the change better

    @property
    def tap_connector(self) -> SQLConnector:
        """The connector object.

        Returns:
            The connector object.
        """
        if self._tap_connector is None:
            self._tap_connector = self.default_connector_class(dict(self.config))
        return self._tap_connector

    @property
    def catalog_dict(self) -> dict:

        ... some code removed to assist with clarity
        
        connector = self.tap_connector

        ... some code removed to assist with clarity

    def discover_streams(self) -> list[Stream]:
        """Initialize all available streams and return them as a list.

        Returns:
            List of discovered Stream objects.
        """
        result: list[Stream] = []
        for catalog_entry in self.catalog_dict["streams"]:
            result.append(
                self.default_stream_class(
                    tap=self,
                    catalog_entry=catalog_entry,
                    connector=self.tap_connector
                )
            )

        return result

An example of this working in a tap can be found in tap-mssql--buzzcutnorman:tap.py