[FEATURE] Take in custom password to run integration tests

[derek-ho]

Is your feature request related to a problem?
Currently tests are run based on a hard coded admin credential. This feature proposal is to move towards a way to provide this dynamically, via flag/user input when running the test. This will help with a few things:

• Running integration tests on your local, in which your local cluster's admin credentials do not match
• CI running with implicit assumptions about the admin credentials

What solution would you like?
A way to pass in admin credentials and to use them within the plugin's integration tests.

What alternatives have you considered?
None

Do you have any additional context?
https://github.com/opensearch-project/security-dashboards-plugin/blob/main/test/constant.ts#L26
integration-test workflow, which only works if password is admin

[derek-ho]

[Triage] This is a change we will make/accept contributions for.