US keyboard layout is incorrectly selected by default for some languages

Originally created by @intrigeri on #12638 (Redmine)

• As discovered on #16838 (closed) and #15161 (closed), selecting Arabic language leads to an English (US) keyboard being selected.
• As discovered on #16481 (closed), selecting Indonesian language leads to an Arabic keyboard being selected.
• As discovered on #12547 (comment 41047), selecting some languages (lang codes: ayc, bhb, brx, cmn, hak, hne, lij, lzh, mhr, nan, nhn, quz, sgs, shs, tcy, the, unm, wae, yue) confuses the algorithm, triggers an exception (invisibly to the user), so English (US) layout is picked by default, and then:
  • one can still choose their preferred keyboard layout by hand, and it’ll be applied as expected;
  • if one selects another language/region, then the previously set keyboard layout is not updated accordingly.

Feature Branch: bugfix/12638-wrong-language-to-keyboard

Related issues

• Related to #12547 (closed)
• Related to #12598
• Related to #14544 (closed)
• Related to #16481 (closed)
• Has duplicate #15161 (closed)
• Has duplicate #16838 (closed)