Parse test instances from test XMLs.

Parse and store test instance arguments for each test. Test instance
arguments is a String -> String value mapping that may have test case
specific meaning. Parsed test instances match exacly test instance
declarations in the test descriptor XML, i.e. tests with no declared
instances will have no instance arguments, and a test with multiple
identical test instance declarations will have multiple identical
instances.

Bug: 18982383
Change-Id: Ia2cc3d05ecdfaeeca04bda862fdd386474118b89
3 files changed