Enable source line info in StableHLO (#5203)
* Enable source line info in StableHLO
* Enable StableHLO with debug info with XLA_HLO_DEBUG flag
* Add user guide in doc string
* Add stablehlo dump test to run_tests.sh and add source line info check
* move stablehlo dump test to new 'stablehlo' folder, update API index
