Make ArrowFlightConfig verifyServer true by default

[BryanCutler]

Description

The ArrowFlightConfig verifyServer was currently defaulting to NULL, we should explicitly set the default to "true" so that when a certificate is supplied in the config, the client will verify the server. See discussion at #24504 (comment)

Also to make integration testing with the native Arrow connector, this adjusts the testing Arrow connector and catalog name to arrow-flight and arrowflight to match. A test property can be supplied to set worker count to 0 for the testing ArrowFlightQueryRunner to run with native workers.

Motivation and Context

The verifyServer config should be a concrete value to ensure the client connection is secure.

Aligning with native Arrow Flight connector in progress at #24504 will make integration testing easier.

Impact

The ArrowFlightConfig verifyServer and server-ssl-enabled are no longer nullable and verifyServer will default to "true".

Test Plan

Existing tests run with the new connector name and ignore the worker count override to use the default.

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