Add InputMessageBuilder to InputEventBuilders.h

Added InputMessageBuilder to InputEventBuilders. InputMessageBuilder
helps to reduce the need to implement test specific structs that stub
InputMessage as is the case in Resampler_test.

Bug: 297226446
Flag: EXEMPT refactor
Test: TEST=libinput_tests; m $TEST && $ANDROID_HOST_OUT/nativetest64/$TEST/$TEST --gtest_filter="ResamplerTest*"
Change-Id: I82103a412461ca835c797e396ca31bb6adf91e4a