Use EventEntry fields as defaults for DispatchEntry

When DispatchEntry is getting constructed, set some of its fields to
the equivalents from EventEntry.

Otherwise, currently, these are set to invalid values (0), which causes
confusion during development.

Bug: 211379801
Test: TEST=inputflinger_tests; m $TEST && $ANDROID_HOST_OUT/nativetest64/$TEST/$TEST
Change-Id: Iddde9e7683caa94c2c1d7a1d8dfef1487ed67ba4