Start SystemConfig parsing before loading libandroid_servers

SystemConfig parsing can be expensive (>100ms), and is currently queued
to a worker thread to avoid blocking the main system server thread
during init. However, it's often needed before parsing is finished, so
the main thread bottlenecks anyway.

Move the async parsing trigger to *before* the native library loading of
libandroid_servers. This should be safe as SystemConfig relies on only
basic APIs that shouldn't need the system server native lib to complete.

On low-end devices, this can reduce boot times by ~500ms. On more recent
flagship devices, this can reduce boot times by ~100ms.

Bug: 383869534
Test: presubmit + boot
Flag: android.server.early_systemconfig_init
Change-Id: Iaf8a09316715a0b31512fdcffca11db1e232beea