core-services/prow/02_config: Enumerate multi-count names

The names are used for custom resources, so we need unique names for
each entry [1].  Consuming jobs will have to split on the --, which is
hopefully unique enough, to get the raw name (if they plan to use it
to select a region or similar).  I'm not using '-', because:

a. I wanted to avoid enumerating single-count entries.
b. I wanted consumers to not have to care about whether they were
   drawing from a single-count or multi-count entry.

Using a separator that is not part of the raw names means that
consumers can always split on that separator without having to worry
about whether they were drawing from a single-count or a multi-count
name.

[1]: #12589 (comment)

Author: wking

core-services/prow/02_config/generate-boskos.py

@@ -67,7 +67,13 @@
     else:
         resource['names'] = []
         for name, count in sorted(data.items()):
-            resource['names'].extend([name]*count)
+            if '--' in name:
+                raise ValueError('double-dashes are used internally, so {!r} is invalid'.format(name))
+            if count > 1:
+                width = len(str(count-1))
+                resource['names'].extend(['{name}--{i:0>{width}}'.format(name=name, i=i, width=width) for i in range(count)])
+            else:
+                resource['names'].append(name)
     config['resources'].append(resource)
 
 with open('_boskos.yaml', 'w') as f: