Updates health check endpoint to include triggerer status

[daniel-anya]

This PR updates the health endpoint to include the triggerers status in its response. The status and latest_triggerer_heartbeat sections will be null for deployments that do not include a triggerer component.

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[boring-cyborg]

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[potiuk]

It also needs updating the docs https://airflow.apache.org/docs/apache-airflow/stable/logging-monitoring/check-health.html

[daniel-anya]

It also needs updating the docs https://airflow.apache.org/docs/apache-airflow/stable/logging-monitoring/check-health.html

Thank you! Added here - 6222c58

[potiuk]

static checks need fixing though

[daniel-anya]

static checks need fixing though

@potiuk Thank you! Should be all fixed now.

[daniel-anya]

I'm seeing this new static check error even though I did not make any changes to this file

Run mypy for core......................................................................Failed
- hook id: run-mypy
- exit code: 1

airflow/sensors/base.py:106: error: Name "Iterable" is not defined 
[name-defined]
        valid_modes = ["poke", "reschedule"]  # type: Iterable[str]
        ^
airflow/sensors/base.py:106: note: Did you forget to import it from "typing"? (Suggestion: "from typing import Iterable")
Found 1 error in 1 file (checked 1022 source files)

[potiuk]

Seems other PRs have the same - looks like new mypy is more picky

[potiuk]

Rebased after merging a fix.

[boring-cyborg]

Awesome work, congrats on your first merged pull request!