mimir-distributed: allow components to override their container image

[narqo]

What this PR does

The PR updates the Helm chart to allow an individual component to override its container image reference via the component's local values. E.g.

# values.yaml

ingester:
  image:
    repository: registry.example/mimir-ingester
    tag: blah-blah

The order in which the values take precedence is:

1. take the component's local image or tag if defined
2. take the image defined in the enterprise section if enterprise is enabled
3. take the globally-defined image otherwise

Which issue(s) this PR fixes or relates to

Fixes #10237

Checklist

• Tests updated.
• Documentation added.
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX].
• about-versioning.md updated with experimental features.

[dimitarvdimitrov]

can you also include the keys in the values.yaml? Since we still want to use the top-level image, then you can make the new <component>.image be a comment. Something like the TSC examples

mimir/operations/helm/charts/mimir-distributed/values.yaml

Lines 873 to 883 in fc8af05

	# -- topologySpreadConstraints allows to customize the default topologySpreadConstraints. This can be either a single dict as shown below or a slice of topologySpreadConstraints.
	# labelSelector is taken from the constraint itself (if it exists) or is generated by the chart using the same selectors as for services.
	topologySpreadConstraints:
	maxSkew: 1
	topologyKey: kubernetes.io/hostname
	whenUnsatisfiable: ScheduleAnyway
	# minDomains: 1
	# nodeAffinityPolicy: Honor
	# nodeTaintsPolicy: Honor
	# matchLabelKeys:
	# - pod-template-hash

that's basically the only documentation we have of helm chart features (plus the changelog, which is barely documentation)

[dimitarvdimitrov]

i've been trying to make the changelog enough for anyone to get the gist of a change and know how to use it. Can you give an example of overriding the image for a component? Something like ingester.image.tag and ingester.image.repository. Or explain that there's an image object under all component objects now

[dimitarvdimitrov]

componentSectionFromName errors out if the component doesn't exist, so i think component isn't optional