refactor: connectors can launch themselves; deprecate: AirbyteEntrypoint and launch(), add SerDe methods on critical protocol classes

[Aaron ("AJ") Steers (aaronsteers)]

Request: Early Feedback.

Goal here is to detangle the tightly-coupled interdependencies:

• AirbyteEntrypoint class
• launch() method
• Connector and Source classes themselves.

Enumerated changes:

• parse_cli_args() made a dedicated helper function. Moved to its own utils module, ensuring no circular dependencies between the airbyte_entrypoint module and the connector class modules.
• All Connector classes inherit class method called launch_with_cli_args()
• The launch() function is deprecated (but not removed).
  • Internally, launch() it is now implemented via source.launch_with_cli_args() Calling it will emit a deprecation warning.
• Goal is to fully deprecate and remove AirbyteEntrypoint (although probably not in this iteration).

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Context

I finally accepted taking on this work, as it is needed to unblock:

• feat(cli): add docker mode when running FAST tests via CLI #524

The problem is: the AirbyteEntrypoint currently gatekeeps access to the connector class itself. And AirbyteEntrypoint doesn't have flexibility into calling results into memory vs pushing results to STDOUT.

Related: the airbyte_cdk.test.entrypoint_output.EntrypointOutput in some ways tries to mitigate this, but it has to in some cases fully re-invent the AirbyteEntrypoint implementation.

And since neither of these gives any flexibility in modes of execution or control of RAM overflow, this PR consolidates the execution to have fewer parts, with the (hopefully) the right interface layers to accomplish execution with minimal wheel-reinventing for callers.