Hide sensitive connection args

[StpMax]

Description

This PR allows to hide sensitive information from:

• engine connection arguments
• model 'using' arguments
• database connection arguments

By default any listed arguments will be replaced with '******'. This behavior can be controlled by setting the show_secrets variable:

set show_secrets=true;  -- by default
set show_secrets=false;

Also, the connection_args and connection_args_example are extracted from the file with the handler and saved in a separate file. This allows us to process the arguments even if the handler cannot be imported.

https://www.loom.com/share/630eec6626fc4e5c9b384504080b4541

Close #8623

Doc issue #9209

Type of change

(Please delete options that are not relevant)

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ⚡ New feature (non-breaking change which adds functionality)
• 📢 Breaking change (fix or feature that would cause existing functionality not to work as expected)
• 📄 This change requires a documentation update

Verification Process

To ensure the changes are working as expected:

• Test Location: Specify the URL or path for testing.
• Verification Steps: Outline the steps or queries needed to validate the change. Include any data, configurations, or actions required to reproduce or see the new functionality.

Additional Media:

• I have attached a brief loom video or screenshots showcasing the new functionality or change.

Checklist:

• My code follows the style guidelines(PEP 8) of MindsDB.
• I have appropriately commented on my code, especially in complex areas.
• Necessary documentation updates are either made or tracked in issues.
• Relevant unit and integration tests are updated or added.

[ZoranPandovski]

The only concern I have is that this PR affects all integrations and we don't have tests to verify if they work. Let me run some of the old health checks that we had for more then 30 integrations on this branch

[StpMax]

@ZoranPandovski it does not change integrations itself, only move connection_args outside from handler's file, so should not break anything

[ZoranPandovski]

Yes, it only affects the GUI form, so e2e tests on GUI work with this PR. We can merge it