Forward enb.xlog to another fluentd or fluentbit server using fluentd's
forward protocol.

Currently, TLS is enabled and a pre-shared secret key is used for
authentication, but certificate verification is disabled.

* Rename mme software type to core-network since mme is a 4G terminology
* Rename template-lte-XXX to template-XXX since lte is a 4G terminology

* Remove gnb-epc and enb-epc software types and merge mme and epc together

Use slapos.recipe.template instead of slapos.recipe.template if possible

Harmonize template keys :
rendered -> output
template -> url
template = inline: -> inline =

Delete "mode" key

See merge request nexedi/slapos!1151