[Oracle] Parse sets lazily to slash importer peak memory

- Add a raw JSON scanner that splits the document into per-set byte ranges
  without materializing the JSON tree
- Keep only the raw document bytes and parse one set at a time in startImport
- Take readSetsFromByteArray by value so the wizard's buffer is moved, not copied
- Clear the retained raw data in releaseSetData()/clear()
- Cover the scanner and lazy parsing with tests

Took 2 minutes

tests/oracle/CMakeLists.txt

@@ -11,7 +11,7 @@ add_test(NAME parse_cipt_test COMMAND parse_cipt_test)
 # Oracle importer unit tests
 add_executable(
   oracle_importer_test ${VERSION_STRING_CPP} ../../oracle/src/oracleimporter.cpp ../../oracle/src/parsehelpers.cpp
-                       oracle_importer_test.cpp
+                       ../../oracle/src/raw_json_scanner.cpp oracle_importer_test.cpp
 )
 
 if(NOT GTEST_FOUND)
@@ -51,7 +51,7 @@ endif()
 add_executable(
   oracle_importer_benchmark_test
   ${VERSION_STRING_CPP} ../../oracle/src/oracleimporter.cpp ../../oracle/src/parsehelpers.cpp
-  oracle_importer_benchmark_test.cpp ${_ORACLE_BENCH_EXTRA_SOURCES}
+  ../../oracle/src/raw_json_scanner.cpp oracle_importer_benchmark_test.cpp ${_ORACLE_BENCH_EXTRA_SOURCES}
 )
 
 if(NOT GTEST_FOUND)