Add openai client config arguments

[alejandrodnm]

This PR continues the work from #219 . That PR was deemed to big so we are splitting the functionality in smaller PRs.

feat!: consolidate OpenAI client configuration

BREAKING CHANGE: Replace individual client configuration parameters with
a single client_config parameter. The base_url parameter has been
moved into the new configuration structure.

• Add new ai.openai_client_config() function to generate client
  configurations
• Remove base_url parameter from all OpenAI functions
• Add client_config parameter to all OpenAI functions
• Support additional client options: timeout, organization, project,
  max_retries, default_headers, default_query

Migration:
Old:

  SELECT ai.openai_embed(
    model => 'model',
    input_text => 'text',
    base_url => 'url'
  );

New:

  SELECT ai.openai_embed(
    model => 'model',
    input_text => 'text',
    client_config => ai.openai_client_config(base_url => 'url')
  );