Function glean_ffi::glean_flush_rlb_dispatcher

#[no_mangle]
pub extern "C" fn glean_flush_rlb_dispatcher()

Try to unblock the RLB dispatcher to start processing queued tasks.

Note: glean-core does not have its own dispatcher at the moment. This tries to detect the RLB and, if loaded, instructs the RLB dispatcher to flush. This allows the usage of both the RLB and other language bindings (e.g. Kotlin/Swift) within the same application.