ArduPilot / MethodicConfigurator / 23689875971

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fix(io): use atomic writes for .param, JSON, and settings files

All file-writing operations used a simple open("w") → write() pattern.
If the application crashes or power is lost mid-write, the target file
is left truncated or empty. This is especially dangerous for .param
files (incomplete parameter sets uploaded to a flight controller could
cause unpredictable behavior) and vehicle_components.json (corrupted
components file breaks all derived parameter computations on startup).

Add a safe_write() utility that writes to a temporary file in the same
directory, then atomically replaces the target via os.replace(). The
utility also flushes and fsyncs before replacing, and preserves file
permissions from the original target.

Apply safe_write to the four most critical persistence paths:
- ParDict.export_to_param() — .param files
- FilesystemJSONWithSchema.save_json_data() — JSON data files
- ProgramSettings._set_settings_from_dict() — settings.json
- VehicleComponents.save_component_templates_to_file() — templates

Update all save-related tests to patch safe_write directly and verify
written data content via captured callbacks.

Closes #1428

Signed-off-by: Yash Goel <yashhzd@users.noreply.github.com>

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