[WIP] Improve rendering status e2e validation

[karlkfi]

• Test the actual API output, instead of using an internal nomos CLI function.
• Validate source and sync status too, to ensure other errors aren't being populated.
• Validate the Syncing status condition values too

[google-oss-prow]

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[google-oss-prow]

@karlkfi: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
kpt-config-sync-presubmit-e2e-multi-repo-test-group3	be71932	link	true	/test kpt-config-sync-presubmit-e2e-multi-repo-test-group3

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[karlkfi]

This PR is blocked on #260 to make the Syncing condition consistently expose errors.

[mikebz]

curious if this is still WIP or if it's even relevant. If it is consider closing the PR and keeping the private branch or converting to draft.