connector_type choice list is duplicated in dwdm and patch_panel with no way to share it #87

Context. extensions/dwdm/dwdm.yml and extensions/patch_panel/patch_panel.yml each
carry a byte-identical 28-choice connector_type Dropdown. The two have already drifted
once (one side went optional, the other did not). Infrahub 1.11.0 cannot share a choice
list across extension files without a shared generic in a common ancestor, and there is no
edge to inherit along: extensions/dwdm depends on extensions/sfp,
extensions/patch_panel on base only.

Per ruling R6 the review takes the cheap half now and defers the real fix. Landed in #75:
the three choices that a stale 4096-char FIXME had commented out are restored in both
files (urm_p4, urm_p8, splice), and both lists carry a sync note:

extensions/dwdm/dwdm.yml:25-27
      # NOTE: this choice list is duplicated in extensions/patch_panel and the two must be
      # kept in sync. Infrahub cannot share a choice list across extension files without a
      # shared generic in a common ancestor, which is a base-tier change.

(and the mirror of it at extensions/patch_panel/patch_panel.yml:25-27).

What this asks for. Introduce a shared generic, e.g. DcimGenericConnectorInterface
carrying connector_type, in a common ancestor both extensions can inherit from, and
delete both duplicated lists plus their sync notes. The reason this was not done in #75:
the only common ancestor available is base/dcim.yml, so the change puts a 28-choice
fibre-connector enum into the base schema every user loads whether or not they own a patch
panel. That is a base-tier addition justified by two extensions, and it should be decided
on its own rather than riding in on a consistency cleanup. The two alternatives considered
and rejected: leave duplicated with no note (they drift again), or make one extension
depend on the other (couples two unrelated extensions and forces DWDM kinds on anyone
modelling a copper patch panel).

Origin: pass-1 review of #75, packet CONN-02, ruling R6.