platform: add the `a_no_auto_noprefixroute` flag

`nm_platform_ip_address_sync()` likes to add IFA_F_NOPREFIXROUTE flag
for all addresses, regardless of `a_ifi_flags` property. By setting this
boolean, that automatism can be suppressed, and the noprefixroute flag
does not get added automatically.

NetworkManager/NetworkManager!1307
56 jobs for noprefixroute in 30 minutes and 39 seconds (queued for 4 seconds)
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