Sync `Environment` via `IScopeObserver` in Hybrid SDK scenarios (sentry-java)

[jamescrosswell]

Follow-up to #5385 to cover sentry-java.

Sync SentryOptions.Environment during hybrid-SDK Init.
Sync Scope.Environment with the hybrid SDK via IScopeObserver.

For sentry-java (Android).

The equivalent work for sentry-native and sentry-cocoa was tracked in #5385 and delivered in:

• feat: sync environment to the native layers #5365 — feat: sync environment to the native layers
• fix: fetch default attributes from Scope first #5376 — fix: fetch default attributes from Scope first

This issue tracks the remaining sentry-java layer, which was explicitly deferred in that work.

[linear-code]

NET-740