Add support for overriding keyboard layout for a keyboard

Default use case for keyboard should follow H/W country code
or IME language, but for special cases like emulator where we
would like to set keyboard layout based on the host device which
is independent of the underlying IME configuration.

Bug: 389995108
Test: manual with emulator
Flag: EXEMPT bugfix
Change-Id: I2baee5037c6dc45724909c5b6d2cac399ce394f5