KGCL yaml statistics output should be deterministic

[matentzn]

Running somthing like

runoak --stacktrace -i simpleobo:ontologies/maxo_2022-06-24.obo diff -X simpleobo:ontologies/maxo_2023-03-09.obo --statistics -o stats/maxo_diff.txt.yaml

Results in non deterministic serialisation of stats/maxo_diff.txt.yaml.

[cmungall]

we should never do yaml.dump(obj) always specify sort keys false

[cmungall]

it turns out that sort_keys=False doesn't fix - on reflection, not unexpectedly, this is a key-value list whose ordering is not defined by the main schema

if we want canonical ordering we have to define it. We can explicitly add ranks to the schema but this is hard for evolution (e.g. when inserting a new type). I suggest something simple like depth first pre-order of the kgcl is-a hierarchy, with alphabetic sorting for sibs