[sujandumaru]

Describe your changes

This adds File -> Import ISOXML. It reads the device description out of an ISOXML TASKDATA.XML and loads it as a DDOP, so a device exported from an FMIS or by our own Export as ISOXML can be edited again.

• If the file holds more than one device, a popup asks which one to load.
• A bad file shows its errors in a popup and the open pool is kept. Values out of range and text too long for the chosen TC version are rejected, not truncated.
• tinyxml2 is added as a submodule for the XML parsing.
• The example DDOPs moved into examples/, next to a new example TASKDATA.XML.
• Fix a bug where a failed Open used to wipe the open pool, and now it keeps it.

How has this been tested?

New task_data_import_test imports examples/TASKDATA.XML, checks every device and object against the file, and checks the result survives an export and re-import. It also checks that broken files are rejected.

cmake -S . -B build -DCAN_DRIVER=None -DSDL_CCACHE=OFF
cmake --build build
ctest --test-dir build --output-on-failure