rename libvixl to libvixl.com.android.art.debug

With I1889653812a980f6a2e3b6b25e7647f7c5919606, libvixl is not available
to the platform as it is included in the ART APEX. To use the APEX
variant of the library, we use the <name>:<apex_name> notation.

Exempt-From-Owner-Approval: cherry-pick from internal

Bug: 150999716
Test: m
Merged-In: I2206f1c28fc0019c0fd726059aa732145f2998ed
(cherry picked from commit 127eae76)
Change-Id: I2206f1c28fc0019c0fd726059aa732145f2998ed