Use std::vector when sending keyCodes

We are currently sending a raw pointer to keyCodes and a size. The size
is also used for outFlags, but it's not well-documented anyways.

Eventually, we may want to just return the flags instead of returning
the boolean.

For now, though, just change the incoming parameter to a vector to make
it less errorprone.

Bug: 228005926
Test: atest libinput_tests inputflinger_tests
Change-Id: I6cc2f5d9b3b7b7c3c120a779ea4cfb4b06e27d1e