Adds more robust AdSense report dimension support

[nicolasleroy]

Summary:

• Normalizes report dimensions, metrics, filters, and orderBy before calling the AdSense API.
• Validates report dimensions/metrics against AdSense v2-supported values.
• Fixes orderBy formatting to use AdSense API syntax like -ESTIMATED_EARNINGS.
• Supports comma-separated dimension/metric inputs in addition to arrays.
• Expands report dimension types to include more current AdSense v2 dimensions.
• Exposes enum hints in MCP tool schemas so clients can discover valid dimensions.
• Adds explicit support for COUNTRY_NAME, PLATFORM_TYPE_CODE, CUSTOM_CHANNEL_NAME, and CUSTOM_CHANNEL_ID.