Change custom branding top logo configuration

[asteriscos]

Description

Hi team, this pull request changes the custom branding configuration. It changes a few descriptions and adds a new way to change the top header logo in the opensearch_dashboards.yml configuration.

Closes #6774

Checks

Docs building

• Compiles without warnings.

Code formatting and web optimization

• Uses three spaces indentation.
• Adds or updates meta descriptions accordingly.
• Updates the redirects.js script if necessary (check this guide).

Writing style

• Uses present tense, active voice, and semi-formal registry.
• Uses short, simple sentences.
• Uses bold for user interface elements, italics for key terms or emphasis, and code font for Bash commands, file names, REST paths, and code.

[Desvelao]

LGTM!