Utilze 19.0.1 dark/light theming capability infos

[AndyScherzinger]

As a follow-up to the changes made in #6332 utilize the new/to-be-introduced server-side capability values, see issue nextcloud/server#21586 or PRs nextcloud/server#21594 (Nc20) and nextcloud/server#21622 (Nc 19.0.1)

• replace color-element with color-element-bright and color-element-dark
• on (client) dark theme use color-element-dark
• on (client) light theme use color-element-bright
• store color-element-dark and color-element-bright on client-side
• use today's logic Enh/dark theme optimizations #6332 for pre-19.0.1 and the described logic for 19.0.1+
• Utilze 19.0.1 dark/light theming capability infos android-library#462 extend OCCapability in https://github.com/nextcloud/android-library for color-element-dark and color-element-bright

• add info that old logic can be removed once 19.x is EOL