Added Arabic keyboard layout

[k-alnuaimi]

Adds a standard Arabic layout alongside the English ones, plus the plumbing an RTL, caseless language needs:

• Layout gains a layoutDirection, applied by Lp3Keyboard. The Arabic letter rows and backspace render right-to-left; digits, paired symbols and the utility row stay left-to-right.
• Lp3BaseViewModel holds the shared viewmodel logic, with the number, symbol and emoji layers and long-press alternates as parameters. EnBaseViewModel keeps its signature and fills in the EnShared ones.
• Rows 1 and 2 are the standard Arabic rows truncated to 10 keys, so those 20 keys keep their usual positions. The letters that fall off the ends join row 3, which has 8 keys since Arabic needs no shift. Hamza forms, ة and ى are on long-press.
• Number layer keeps Western digits with Arabic punctuation (، ؛ ؟).
• back_lp3 and return_lp3 are autoMirrored, and MultiLabelKey pins its label to LTR so "#+=" doesn't render reversed.

The sample app's text field now follows the active layout's direction.

[dupontgu]

thank you for this!! Gonna take a look Friday/early next week

[dupontgu]

Thanks again for doing this. Technically I think it's perfect, but I got some feedback from a user that the keys were in the opposite order from right to left than they would expect. Does that ring true? I don't think it would be a difficult change. Here's the implementation from this PR vs. a Gboard screenshot: