Reland: Use "gfxstream" namespace

This reverts commit cfcd06b4b39c295f580970b26b50ca979bda7a40.

Reland adds in aosp/2514000 which was only built on the "full"
target.

Bug: b/271464937
Test: android build
Test: cmake build
Change-Id: Ibf6d8bf079157878f1a4b7ca9d2e9dae27467f3b