Add ConfigUpdater service for CT logs

The service extracts the logs from the json log list format and creates
a lookup directory based on conscrypt's CTLogStoreImpl's lookup.

Since we don't have renameat2 yet (3.15 kernels) in order to support
atomic swapping of the log directories on updates a symlink is used
to point to the current directory and then that symlink is atomically
replaced with a symlink pointing to the new directory.

Bug: 28746284
Test: running ConfigUpdater/scripts/test_install.sh with various ctlog
files
Change-Id: I39372aea83aff6d4a72e517eaae7a7c6eac89c57