Added tests to event_source_mapping and alias_ref for namespace reference check

[michaelhtm]

Issue #1777

Description of changes:
*Adding new e2e test suites to validate our recently introduced feature "cross namespace resource references". In order to test this feature, we added a new feature to allow new namespace creation, from which resources will be referenced (alias and event source mapping in this case).

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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This pull-request has been approved by: michaelhtm
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[ack-prow]

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

Test name	Commit	Details	Required	Rerun command
lambda-kind-e2e	3b496ed	link	true	/test lambda-kind-e2e
lambda-verify-attribution	3b496ed	link	true	/test lambda-verify-attribution

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