[FEATURE] OpenSearch logo should inherit from OpenSearch Dashboards branding configuration (and be theme-aware)

[joshuarrrr]

Is your feature request related to a problem?
OpenSearch Dashboards provides users with the ability to customize branding (including logos) via the yaml config file: https://opensearch.org/docs/latest/dashboards/branding/

Logos and marks in this system are "theme-aware" because they use dark/light mode variants appropriately. In contrast, the
security-dashboards plugin provides it's own default OpenSearch logo, as the default, with no light/dark variants or logic:

security-dashboards-plugin/public/apps/login/login-page.tsx

Line 31 in 91faa3d

import defaultBrandImage from '../../assets/opensearch_logo_h.svg';

What solution would you like?

Rather than providing separate default assets, the login page should be refactored to pull the correct default logo assets from the branding service of OpenSearch Dashboards. We should also consider merging and consolidating branding configuration options.

What alternatives have you considered?
A clear and concise description of any alternative solutions or features you've considered.

Do you have any additional context?
Add any other context or screenshots about the feature request here.

[stephen-crawford]

[Triage] Thank you for filing this issue @joshuarrrr. This change is part of broader OUI implementation. Labeling good first issue.

[stephen-crawford]

Closing this as it is part of #1529