chore: Move most configuration out of CoreSocketFactory and into CloudSqlInstance

[hessjcg]

Makes configuration specific to a cloud sql instances instead of part of a global singleton.

This change is small in size because it:

• avoids changes to the public methods of CoreSocketFactory
• avoids breaking existing unit tests with lots of mocks in them

Further work needed:

• Ensure that v2 style socket factory config is properly respected
• Ensure that r2dbc works properly with socket factory configs
• Possibly add more config properties to CloudSqlInstanceKey

[conventional-commit-lint-gcf[bot]]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot https://conventionalcommits.org/