Admin_Settings: Various accessibility improvements

[costdev]

Pull Request

What changed?

• Added aria-describedby to settings elements and a matching id attribute to the .description element.
• Added the label_for argument to add_settings_field() calls to ensure the field labels are wrapped in the <label> tags.
• Changed Clear Log and View Log from a elements to button elements with type="button" so they don't trigger a form submit.

Why did it change?

• To reduce accessibility errors.
• To be more consistent with other settings pages in WordPress.
• Note: There are still 3 errors.
  • An error due to api_host_other not having a label.
  • A contrast error for the transparent text in the "Generate API Key" button
  • A contrast error for Voltron.

Did you fix any specific issues?

Fixes #299

CERTIFICATION

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