Add image strings to intern table

When we create the runtime, we now add the image strings to the
intern table if we are the zygote. This caused some memory bloat,
so I added an extra unordered set to the intern table.

There is now two unordered sets (hash talbe). One for pre-zygote
interns and one for post-zygote interns. This helps since the
pre-zygote hash table doesn't get dirtied. Even with adding
the image strings, we get total memory savings of around 5-7 MB
native PSS after device boot.

FB launch Before:
2.20% art::DexFile::FindStringId(char const*) const
TotalTime: 2069
TotalTime: 1985
TotalTime: 2088
TotalTime: 2003
TotalTime: 2034
TotalTime: 2049
After boot native PSS: 175585 kB: Native

0.27% art::DexFile::FindStringId(char const*) const
TotalTime: 1682
TotalTime: 1756
TotalTime: 1825
TotalTime: 1751
TotalTime: 1666
TotalTime: 1813
After boot native PSS: 167089 kB: Native

Bug: 18054905
Bug: 16828525
Bug: 17808975

Change-Id: Ie367f3222f8c4db409ec49c3845276908b51e9c9
5 files changed