ref(core): Use SDK metadata constants from conventions (#24978)

Uses `SENTRY_RELEASE`, `SENTRY_ENVIRONMENT`, and
`SENTRY_SDK_INTEGRATIONS` from `@sentry/conventions/attributes`.
Deprecates the existing core constants while preserving their public
exports and identical attribute keys; emitted values, defaults, and
serialization remain unchanged.

Part of #24961 / [JS-3868](https://linear.app/getsentry/issue/JS-3868).

Co-authored-by: GPT-6 <codex@openai.com>