Closes #17841 Allows Tags to be displayed in specified order

[jnovinger]

Fixes: #17841

• Adds Tag.weight field so users can specify an ordering weight. Valid values are 0-32767.
• Sets default Tag ordering to ('weight', 'name') so that weights are used for ordering first (lower weights get sorted first) and then names for tie breakers.
• Sets default TaggingMixin.tags ordering to ('weight', 'name') so that weights are used for ordering first (lower weights get sorted first) and then names for tie breakers. Note: this was required so that calls through an objects .tags related manager would be sorted when called from a template (e.g. so that ordering would work for things like {% for tag in Tag.objects.all %})
• Updates existing tests and adds tests for default model ordering and related manager ordering defaults.
• Adds Tag.weight in all the required places.

[arthanson]

Good work @jnovinger everything looks good.