Default load trusted_network auth provider if configured trusted networks

[awarecan]

Description:

Default load trusted_network auth provider if user configured trusted networks

Related issue (if applicable): fixes #

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.github.io#<home-assistant.github.io PR number goes here>

Example entry for configuration.yaml (if applicable):

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[balloob]

I don't know if we should do this, as I actually wanted to put in a PR to migrate the trusted networks config to the trusted network auth provider config before release.

Although this will be less painful migration.

[balloob]

Doing this for now.

In the future we'll do it slowly:

• allow configuring trusted networks under auth provider. If no config in auth provider, check for config under HTTP. If found, use that and print warning that configuration should be put under auth provider
• drop support for config under HTTP