Optimize SystemFeaturesMetadata index lookup

Using a ~150 length string->int switch statement lookup turns out to
be both slower than an equivalent ArraySet lookup, and larger in terms
of code size (both dex + compiled). Switch to using a static ArraySet
(initialized in the zygote) for efficiency.

A follow-up change will add a microbenchmark for further validation.

Bug: 203143243
Test: m + presubmit + compare dex/odex/runtime perf
Flag: EXEMPT refactor
Change-Id: I1231149b928488cb716ec09a33ef1ec4ac7e2785