Carrier config for opportunistic eSIM download only over WiFi

Carrier configuration KEY_OPPORTUNISTIC_ESIM_DOWNLOAD_VIA_WIFI_ONLY
added to control if eSIM should be downloaded via only WiFi or use
both WiFi/Data. True will download esim only via WiFi and false will
use both WiFi and Data connection.

Bug: 217378657
Test: make
Change-Id: I01c0c16293f4e490a1c4c7f521fd454cc045296f