Add ResTable_sparseTypeEntry support

Benchmarks on bullhead-userdebug show that there is a negligent
performance impact when using sparse entries on a 30% loaded
sparse type of 1000 resources.

Benchmark                                             Time           CPU Iterations
-----------------------------------------------------------------------------------
BM_SparseEntryGetResourceSparseLarge                255 ns        254 ns    2751408
BM_SparseEntryGetResourceNotSparseLarge             254 ns        254 ns    2756534

Bug: 27381711
Test: make libandroidfw_tests aapt2_tests
Change-Id: I051ea22f2f6b2bc3696e446adc9e2a34be18009f