Preserve all COMPATIBILITY_SUITES values in module-info

Extend COMPATIBILITY_SUITES in module-info to avoid overwriting previous
values. In particular, this happens for the `host-unit-tests` suite
which is automatically added by Soong rules only to be clobbered by the
modules that have both device and host variants.

Bug: 209806322
Test: source build/envsetup.sh ; lunch aosp_cf_x86_64_phone ;
      m out/target/product/vsoc_x86_64/module-info.json
Change-Id: I56a2d4c9786ed3da1e788ba211ec1bcaa6559549