Convert @ColorLongs in native code

Bug: 120904891
Bug: 122844033
Bug: 122514935
Test: CtsGraphicsTestCases

Only convert rgba. ColorSpace should be converted in Java, so we can
just pass the native pointer and handle potential Exceptions before
going into native code.

Requires a change to external/skia [1] to make SkHalfToFloat SK_API.

[1] https://skia-review.googlesource.com/c/skia/+/185140

Change-Id: I0b42c17159b290868a6bed7b90da096995504c4d