feat: add secrets fetch command to CDK CLI

[devin-ai-integration]

This PR targets the following PR:

• feat: add airbyte-cdk CLI with support for: connector test, secrets fetch and --version #493

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Added a 'secrets fetch' command to the airbyte-cdk CLI that can fetch connector secrets from Google Secret Manager. This provides functionality similar to the PyAirbyte script 'run_gsm_connector_secret_fetch.py'.

The command follows the same patterns as existing commands like 'connector test', allowing users to specify either a connector name or directory.

The Google Secret Manager dependency is added as an optional dependency in the 'dev' extras to avoid adding it as a requirement for production use.

Link to Devin run: https://app.devin.ai/sessions/121e177095fa41d4ae43dcfae597f3de
Requested by: Aaron ("AJ") Steers

[devin-ai-integration]

Original prompt from Aaron:

@Devin - Take a look at the pyairbyte script called `examples/run_gsm_connector_secret_fetch.py`. I want to build the same into a CDK CLI, building on the work from this PR: <https://github.com/airbytehq/airbyte-python-cdk/pull/493>

[devin-ai-integration]

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