Remove unused tag sensor from devices not really using it

[thomluther]

System Health details

None

Integration version

2.1.0

Checklist

• I have enabled debug logging for my installation.
• I have filled out the issue template to the best of my ability.
• This issue only contains 1 issue (if you have multiple issues, open one issue for each issue).
• This issue is not a duplicate issue of any previous issues..

Describe the issue

All devices got a Tag sensor that may show the tag if the device supports tagging like smart plugs do.
Devices not supporting tagging will show an empty sensor.

The cloud Api introduced this additional field for all devices and the Api library as well as the integration picked it up.

Reproduction steps

upgrade to 2.1.0 to see the tag entity for every device

Debug logs

None

Diagnostics dump

No response

[thomluther]

The tag sensor will now be added only if the tag field really has a value set.
Empty strings will be ignored.
Note: There won't be translations for the tags, since it is unknown which kind of tags are supported or may be added in future.

There was also a new tag category implemented with 2.1.0 to exclude the tag field in general.