[Astro] Deprecate passing `Sentry.init()` options to the build-time config in Astro

[lforst]

Description

We have concluded that passing build time config other than (release, env, tunnel, etc.) to runtime Sentry.init() configs, without the users explicitly calling Sentry.init() is a bit of a pattern that introduces intransparent behavior and confusion.

This task is about

• Updating the Astro docs to instead encourage runtime-specific Sentry.init() configs
• Potentially deprecating (no removing) of the build-time pass-throughs in question.