Related to: #9110
* Make `IntegrationReactiveUtils.CONTEXT_SNAPSHOT_FACTORY` instance conditional on the `IntegrationReactiveUtils.isContextPropagationPresent`
to avoid class-not-found problem for the `io.micrometer.context.ContextSnapshot`
* Make `IntegrationReactiveUtils.captureReactorContext()` & `IntegrationReactiveUtils.setThreadLocalsFromReactorContext()`
conditional on the `isContextPropagationPresent`
**Auto-cherry-pick to `6.2.x`**
2225b83957