Add delay before enabling tap while typing on physical keyboard

To improve touchpad palm rejection while typing, this change will add a
delay before tap to click is enabled.
This change add a delay to 400ms, this is based on internal testing
within team, and may be updated after a cafe study with large audiance.

Bug: 301055381
Test: atest inputflinger_tests
Change-Id: Ie582b5932a8bbcdbf479d375a25e16a1c8318253