feat(android): silent install for referred kbd

Relates to #5230, #5219.

[Draft]

Adds a silent parameter to the `downloadKMP` function and makes the
install silent for referred keyboards.

However, this is incomplete:

1. We need to be able to control silent levels:
   * Completely silent
   * Only welcome
   * Full install

2. When silentInstall is true, currently welcome is still shown, but the
   paging controls are not configured correctly and a blank screen is
   shown after install.