ncm-network: refactor network core schema

[stdweird]

Refactors the network core-schema in structure that easier to modify and easier to move to template-library-core. By default nothing changes: the original core-schema (now renamed to core-schema-legacy) is still used.

By setting the variable variable QUATTOR_TYPES_NETWORK_LEGACY = false; before the core-schema is included, you can test the new structure. It should compile and there should be no differences in the generated output.

There is a small chance of backwards incompatibility: some of the network types have been renamed from prefix structure_ to network_, so there is a non-zero chance that this conflicts with self defined types or variables.

[stdweird]

@ned21 @jrha @jouvin ideally i had avoided to use variables inside declaration templates, but i see no other way to control the rollout of these changes.

i am also not yet convinced the backend selection should be implemented like this, but this is not a regular component schema either.

i hope we can get this merged so we can start testing the refactor at least (and then drop the core-schema)

[aka7]

@stdweird Just wondering where we are with this? Are we separating the schemas in approach?

I ask so I can then update this to provide the additional rules param. https://github.com/quattor/configuration-modules-core/pull/1659

[stdweird]

@aka7 euhm, i just force pushed a rebase on master, and now the PR is closed ;)

[stdweird]

@aka7 will reopen.

i have no feedback saying i should modify anything, so waiting for a merge

[stdweird]

@aka7 this is merged as part of #1676

[jrha]

Whoops, I thought I'd merged this first.