SettingProvider: Support customizing the preset values

Some settings are requested to support customizing for some
operator. Preset these values in the SettingProvider and
the default values could be overlay in those operator if
needed:
1. def_input_method - default input method
2. def_enable_input_methods - enabled input methods

Change-Id: I29808752b3a1dccd255ecb39af1960fb7520ed13
CRs-Fixed: 933506