unify commercial / premium fleet checking logic and add a param to diagnostics json

[shawaj]

Currently we have commercial fleet checking logic in a few different places:

• template_hyper.html
• upgrade.html
• device_info.html
• auth.py

We should unify these into a single function and add a parameter to diagnostics JSON (maybe "premium":true or similar) so we can use something like:

{% if diagnostics.premium %}

instead of

{% if diagnostics and diagnostics.BA and diagnostics.BA.endswith('-c') %}

It also means we can make use of similar logic to what is in auth.py whereby we check for the -c at end of fleet name but we also check for the fleet ID as well.

Related to #601 #574 #581