It's default enabled that it waits for border routing establishment
before starting the SRP server. But there are also use cases where
the user may want to know what are the devices in the Thread network
before actually reach to the devices, or it doesn't depend on border
routing to reach to a Thread device.
Given that, this commit adds the support of starting SRP server
without waiting for border routing by adding a new
Runtime Resource Overlay configuration parameter:
config_thread_srp_server_wait_for_border_routing_enabled
Test: it's difficult to assert on the SRP server starts up timing. But manually verified that the SRP server starts without waiting for the routing manager when the RRO config is flipped:
```
01-09 20:18:35.835 7555 7555 I ot-daemon: [I] RoutingManager: RsSender: Sent RS 1/3
01-09 20:18:35.835 7555 7555 I ot-daemon: [I] RoutingManager: Received RS from fe80:0:0:0:98af:44ff:fe2e:fa80 on infra netif 17
01-09 20:18:35.835 7555 7555 I ot-daemon: [I] RoutingManager: Will evaluate routing policy in 00:00.150 (150 msec)
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] NetDataPublshr: DNS/SRP service - State: Adding -> Added
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] SrpServer-----: Start listening on port 53536
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] NetworkData---: Sent ServerData
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] NetworkData---: Received ServerData
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] NetworkData---: Allocated Service ID = 1
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] NetworkData---: Sent ServerData ack
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] Notifier------: StateChanged (0x00000200) [NetData]
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] Mle-----------: Send Data Response (ff02:0:0:0:0:0:0:1)
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] BbrLeader-----: PBBR state: Unchanged
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] BbrLeader-----: Rloc16:0x8800, seqno:69, delay:5, timeout:3600
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] RoutingManager: Will evaluate routing policy in 00:03.558 (3558 msec)
01-09 20:18:35.926 7555 7555 I ot-daemon: [I] NetDataPublshr: DNS/SRP service (state:Added) in netdata - total:1, preferred:0, desired:2
```
Bug: 378587036
Change-Id: Ib768014f3c44dca89390cec823a1c2acac38ab0d
fad62be2d2