Hoist `@sentry/utils` into `@sentry/core` and deprecate all of its exports

[lforst]

Description

We have decided that merging @sentry/utils into @sentry/core will clean up our architecture by quite a bit and prevent footguns like diverging package versions.

This task involves:

• Moving the entirety of @sentry/utils into @sentry/core and re-export everything from @sentry/utils (also implicitly making core not depend on utils anymore) (feat(core): Hoist everything from @sentry/utils into @sentry/core #14382)
• Removing all references to @sentry/utils from docs and replace with @sentry/core (Use @sentry/core instead of @sentry/utils sentry-docs#11890)
• Deprecating all exports in @sentry/utils and instruct to use @sentry/core instead. (feat(utils): Deprecate @sentry/utils #14431)