Remove non-build related astro integration types #16837

Description

Today, we recommend to configure the Astro SDK through client/server config files. Previously, it used to be possible to also pass some runtime config to the astro plugin. We have stopped documenting/recommending this, but it is still possible and typed, leading to potential confusion.

To clean this up, we will:

• Remove all specific types for runtime config from the astro plugin. Only e.g. sourcemaps options will remain typed
• To not break existing setups, the plugin will also accept & Record<string, unknown>.
• We will pass anything unknown through to the SDK and warn that this is deprecated and will be removed in a future version (not v10, though).