Convert requested SDK version if preview API level

The 'sdk_version' flag should be allowed to specify a preview API level
codename. Convert the raw name into an integer using the common library
functions. This also switches out the comparison logic to use the
ApiLevel as defined by the 'android' library instead of doing
string-to-int conversion on the output.

Test: Verified that setting VIC as an sdk_version does not crash.
Change-Id: I6ed5fb7ff0dcfa3598e74faa656cde7fa2085bae