Validate scale and container concurrency options when updating configuration resource

[toVersus]

I would like to do more contributions on knative/client but currently some large PRs are under reviewing. Therefore, I decided to read and refactor current code bases without bothering core contributors. If it's too much troubles, just let me know!

Proposed Changes

• Validate the scale and container concurrency options and returns error when invalid value is found.
• Add unit/e2e tests for handling invalid user inputs
• Use GetContainer method for extracting container spec from revision template
• Use constant values for annotation keys
• Add missing unit test for TestUpdateContainerImage method

Release Note

None

[knative-prow-robot]

Hi @toVersus. Thanks for your PR.

I'm waiting for a knative member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[maximilien]

@toVersus Thanks for contribution. Yes, we have some pending PRs on core and things should clear up next week. Also, PR #274 will require some changes for your e2e but should not be too hard and clean things a bit even more. Leaving some initial review. Cheers 🍻

[sixolet]

/ok-to-test

[rhuss]

@toVersus have you rebased to the latest master commits ? If not, please do as this would fix the integration test error.

[toVersus]

@rhuss Hmm, I have already rebased to the latest master commit, but it seems something wrong with the tests against the latest release job. I rebased to the previous commit and triggered the CI job again.

[toVersus]

@rhuss It looks like an error comes from the flakiness of the test. Now, it's green!
I think this PR is ready for the review because #274 is already merged.

[navidshaikh]

minor typo in error message and few suggestions about using the flag-name in error message than using the annotation key

[knative-metrics-robot]

The following is the coverage report on pkg/.
Say /test pull-knative-client-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/kn/commands/service/configuration_edit_flags.go	78.6%	77.5%	-1.1
pkg/serving/config_changes.go	65.5%	75.8%	10.2
pkg/serving/revision_template.go	80.0%	87.5%	7.5

[toVersus]

@navidshaikh Thanks for reviewing! I addressed your comments.

[rhuss]

Thanks a lot ! lgtm

/approve
/lgtm

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rhuss, toVersus

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