Refine DisplayDeviceInfo#diff.

Currently its diffing is too coarse, leading to confusing double
messages and non-specific logs for common operations like refresh rate
changes. Refine the diff to provide more detail so we can better log
what's going on on the device.

Fixes: 330169828
Flag: EXEMPT logging bug fix
Test: atest DisplayDeviceInfoTest
Change-Id: I6acc91d77b99ef1ae5cf52ba031b88fa70720b24