Add diagnostics support to Fritz

[chemelli74]

Proposed change

Add diagnostics support to Fritz

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.
• Untested files have been added to .coveragerc.

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To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[probot-home-assistant]

Hey there @mammuth, @AaronDavidSchneider, @mib1185, mind taking a look at this pull request as it has been labeled with an integration (fritz) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[mib1185]

The diagnostics download itself works great ✅
example diag data:

{
  "home_assistant": {...},
  "custom_components": {...},
  "integration_manifest": {
    "domain": "fritz",
    "name": "AVM FRITZ!Box Tools",
    "documentation": "https://www.home-assistant.io/integrations/fritz",
    "requirements": [
      "fritzconnection==1.8.0",
      "xmltodict==0.12.0"
    ],
    "dependencies": [
      "network"
    ],
    "codeowners": [
      "@mammuth",
      "@AaronDavidSchneider",
      "@chemelli74",
      "@mib1185"
    ],
    "config_flow": true,
    "ssdp": [
      {
        "st": "urn:schemas-upnp-org:device:fritzbox:1"
      }
    ],
    "iot_class": "local_polling",
    "loggers": [
      "fritzconnection"
    ],
    "is_built_in": true
  },
  "data": {
    "entry": {
      "entry_id": "35b5195b73e7bf2295de44d5fdc8e47a",
      "version": 1,
      "domain": "fritz",
      "title": "FRITZ!Box 7530 AX",
      "data": {
        "host": "192.168.1.1",
        "password": "**REDACTED**",
        "port": 49000,
        "username": "**REDACTED**"
      },
      "options": {
        "consider_home": 5
      },
      "pref_disable_new_entities": false,
      "pref_disable_polling": false,
      "source": "user",
      "unique_id": null,
      "disabled_by": null
    },
    "device_info": {
      "model": "FRITZ!Box 7530 AX",
      "current firmware": "256.07.29",
      "latest firmware": "",
      "update available": false,
      "is router": true,
      "mesh role": "master",
      "last update success": true,
      "last exception": null
    }
  }
}

But getting the tests working requires a lot more effort and love , since it is the first time for this integration, that the whole configuration entry setup needs to be mocked, which needs the login, gatting device-info, gathering available services, getting host-infos and connected clients,...