added API key feature in gfconfig forms

Title

Added API Key Field in GFConfig Forms

If this fixes a bug or resolves an issue, provide a link to that issue. Give a detailed description that answers:

Brought back API key field in GFConfig firms, user can now create grafana instance either with username/password or API key

Put an x in the boxes that apply

[x] Feature (non-breaking change which adds functionality)
[ ] Bug Fix (non-breaking change that fixes an issue)
[ ] Breaking Change (feature/fix that causes existing features to not work as expected)
[ ] Documentation

[x] I have read the [contribute]contributing doc
[x] Classes, scripts, and environment variables follow existing naming convention
[x] Lint and Unit tests pass locally
[x] New features on hardware have been tested on a local Raspberry Pi
[x] Mention new programs/binaries if any must be installed along with this change
[x] Mention new environment variables if any have been added to hardware/env file
[x] Please make sure test coverage does not drop. If it does, please explain the reasons.
[x] Any new required python modules are added to the requirements.txt