refactor: use directional isolation instead of locale RTL label

[Samillion]

Changes:

• Use directional isolation to show RTL locale tooltips correctly instead of setting direction into each locale set
  • Replaces relying on \fe-1 as it is generally not recommended.
• Remove lang_direction from all locales
• Remove lang_direction from locale docs

Reference: https://www.unicode.org/reports/tr9/#Explicit_Directional_Isolates

Based on: mpv-player/mpv#17606

Their implementation requires more consideration (ie: native context menu). However, for this use case just for tooltips, it should suffice.