dev -> main

get rid of need for FEATURE_PROMETHEUS_EXPORTER_ENABLED to be present in ci-test.py settings file

Merge this PR to `main` branch to start another [github actions
job](https://github.com/grafana/oncall/blob/dev/.github/workflows/helm_release.yml)
that will release the updated version of the chart (version: 1.2.42,
appVersion: v1.2.42) into `grafana/helm-charts` helm repository.

This PR was created automatically by this [github
action](https://github.com/grafana/oncall/blob/dev/.github/workflows/helm_release_pr.yml).

Co-authored-by: GitHub Actions <[email protected]>

Merge dev to main

v1.2.44

Merge: Release oncall Helm chart 1.2.44

Co-authored-by: Michael Derynck <[email protected]>
Co-authored-by: Joey Orlando <[email protected]>
Co-authored-by: Matias Bordese <[email protected]>
Co-authored-by: Rares Mardare <[email protected]>
Co-authored-by: Joey Orlando <[email protected]>
Co-authored-by: Ildar Iskhakov <[email protected]>
Co-authored-by: Ruslan Gainanov <[email protected]>
Co-authored-by: Yulia Shanyrova <[email protected]>

# What this PR does

## Which issue(s) this PR fixes

## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [ ] Documentation added (or `pr:no public docs` PR label added if not
required)
- [ ] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)

# What this PR does

## Which issue(s) this PR fixes

## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [ ] Documentation added (or `pr:no public docs` PR label added if not
required)
- [ ] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)

[css fixes, displaying chatops button visibility fix]

- Enabling existing secrets for external MySQL and Redis
- Tolerate existing secrets for bundled charts.
- README.md: secrets handling explained.
- Fixed multiple bugs where missing required field was replaced with
  default instead of failing.
- PHONE_NOTIFICATIONS_LIMIT was on the wrong level: it was not set if
  existingSecret was true.

Next are the cosmetic changes. They improve chart consistency, e.g.
prevent generation of multiple new lines in certain cases:
- Common approach to spaces trimming. This typically allows curly blocks
  and actual strings indentation and nice `nindent` usage:
  - Two curly blocks should not trim the same space. I.e.
    "{{ ... -}} {{- ... }}" shouldn't happen.
  - Template generates either single line or multiline string. In both
    cases, no new line appears on both sides of the output string. So we
    delete unnecessary new lines inside and at the end of string with
    "trim-to-left" (`{{-` ) and the leading new line using
    "trim-to-right" (`-}}`).
    Note that trimming both leading and trailing new line is not
    always easily possible:
    Masterminds/sprig#357

    Example.

    ```
    {{- define "mytemplate" -}}
    {{ if someBoolean -}}
      {{ .Value.some }}
    {{- else -}}
      some string
    {{- end }}
    {{- end }}
    ```

- `template` replaced with `include`. It is often recommended to use
  `include` by default, as it allows pipelining.