Add support for float-to-int in the optimizing compiler.

- Add support for the float-to-int Dex instruction in the
  optimizing compiler.
- Factor type conversion related lines in
  compiler/optimizing/builder.cc.
- Generate x86, x86-64 and ARM (but not ARM64) code for
  float to int HTypeConversion nodes.
- Add related tests to test/422-type-conversion.

Change-Id: I2382dfc04bf394ed75f675148cfcf98216d65bc6