* Make JsonishParser use utils::Status
- add unsupported error in utils::Status
- add invalid case in the test
* return a pair of Status and string in resolveEscapes;
use initializer list for JsonishString and move that to the header.
* Use utils::Status in MaterialParser
* Use utils::sstream instead of std::stringstream
* Remove remaining std::cerr and dep; update MaterialParser::reflectParameters
* make error message in utils::Status more generic
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Co-authored-by: Powei Feng <powei@google.com>
