Make node_id globally unique (again)

[evetion]

Fixes #1690 as a 🎁 for @deltamarnix when he is back from holiday.

Triggered by #1648, which seems very hard to do in QGIS as it doesn't support compound indexes and we dislike a separate global unique id. In a discussion with @visr he mentioned most people don't use the non-global unique id feature (yet).

Reverts #1513. Partially reverts #1690 as the NodeID changes are not reverted, as it is quite useful to know the node_type in several parts of the code (instead of only a node_id). Therefore, I've added a new NodeID constructor and joined the Edge table with the Node table.

I had to change the node_ids of several new test models created by @SouthEndMusic, bit of a pain, but the tests seem to pass still.

Furthermore, I changed the node.add functionality to return the NodeData, which should make the edge.add more straightforward (and pave the way for automatic id numbering in the future). So this:

model.terminal.add(Node(terminal_id, Point(500, 200)))
model.tabulated_rating_curve.add(
    Node(6, Point(450, 200)),
    [tabulated_rating_curve.Static(level=[0.0, 1.0], flow_rate=[0.0, 10 / 86400])],
)

model.edge.add(
    model.basin[6],
    model.tabulated_rating_curve[6],
)
model.edge.add(
    model.tabulated_rating_curve[6],
    model.terminal[terminal_id],
)

becomes this:

term = model.terminal.add(Node(terminal_id, Point(500, 200)))
trc0 = model.tabulated_rating_curve.add(
    Node(0, Point(450, 200)),
    [tabulated_rating_curve.Static(level=[0.0, 1.0], flow_rate=[0.0, 10 / 86400])],
)

model.edge.add(
    basin6,
    trc0,
)
model.edge.add(trc0, term)

I've made this change in a single Python test model, and in the first model of the examples notebook. We could gradually change this further over time.

[evetion]

Given my frustration with renumbering some odd models, I've added automagic numbering of NodeIDs to this PR, which also includes quicker validation:

model.terminal.add(Node(1, Point(500, 200)))
model.terminal.add(Node(1, Point(500, 200)))  # will now error (before only when writing)

And do the following to get automagic numbering (you have to specify the geometry kwarg for constructor reasons, best to move to fully named arguments in the future):

term = model.terminal.add(Node(geometry=Point(500, 200)))
assert term.node_id == 1

[visr]

Great work! Left some comments.