feat(charts): add global.imageRegistry parameter

[LKummer]

Pull Request template

Why is this PR required? What issue does it fix?:

Fixes #203.

What this PR does?:

• Adds global.imageRegistry Helm parameter for specifying an image registry to be used for all images. It is overridden by localpv.image.registry and helperPod.image.registry when specified.
• Adds support for specifying image registries without a trailing /, while still supporting a trailing / to avoid breaking existing configurations.

Does this PR require any upgrade changes?:

No.

If the changes in this PR are manually verified, list down the scenarios covered::

• Installation with default values.
• Installation with global.imageRegistry set without trailing /.
• Installation with global.imageRegistry and localpv.image.registry set without trailing /.
• Installation with global.imageRegistry and helperPod.image.registry set without trailing /.
• Installation with global.imageRegistry, localpv.image.registry and helperPod.image.registry set without trailing /.
• Installation with localpv.image.registry set with trailing /.
• Installation with helperPod.image.registry set with trailing /.

Any additional information for your reviewer? :
Mention if this PR is part of any design or a continuation of previous PRs

No.

Checklist:

• Fixes Helm chart should read image registry name from global.imageRegistry variable #203
• PR Title follows the convention of <type>(<scope>): <subject>
• Has the change log section been updated?
• Commit has unit tests
• Commit has integration tests
• (Optional) Are upgrade changes included in this PR? If not, mention the issue/PR to track:
• (Optional) If documentation changes are required, which issue on https://github.com/openebs/openebs-docs is used to track them:

[LKummer]

I tried to force push to re-run the CI job, it seems to have failed before installing the chart in the integration test.

[tiagolobocastro]

I suspect we need something like this: https://github.com/openebs/lvm-localpv/pull/357/files

[tiagolobocastro]

CC @niladrih

[niladrih]

CI check fails due to CI issue. Fix: #229.

[niladrih]

@LKummer could you please rebase your branch? The CI should run better after the recent changes.

[LKummer]

Thank you @niladrih, I've rebased my branch.

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 37.35%. Comparing base (cab53c4) to head (0657f34).
Report is 14 commits behind head on develop.

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Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #227      +/-   ##
===========================================
- Coverage    37.91%   37.35%   -0.57%     
===========================================
  Files           36        1      -35     
  Lines         3373      779    -2594     
===========================================
- Hits          1279      291     -988     
+ Misses        2012      479    -1533     
+ Partials        82        9      -73     

Flag	Coverage Δ
integrationtests	37.35% <ø> (?)

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[tiagolobocastro]

This would be good to have on all openebs charts

[niladrih]

Thanks for this change @LKummer. I'll merge when you resolve the review conversation (as in click on the 'Resolve conversation' button, up to you if you'll take the suggestion or not).