Add Joystick Gremlin profile import for Advanced Mapping

[mojouto3]

Summary

• Adds "Import from Joystick Gremlin..." to the Advanced Mapping tab: pick a Gremlin profile .xml file, match each Gremlin device to a connected controller, pick which mode to import as the profile's normal behavior, and import.
• Deliberately best-effort, not full Gremlin parity: MIM's Rules UI only exposes "Normally" plus one level of "While holding X" conditions by design (an earlier full modes/bindings UI was rejected as recreating Gremlin's own confusing complexity). Imports what has a real MIM equivalent:
  • remap (button/axis to vJoy) -> Single Press / positional axis
  • tempo containers -> Tempo (tap/hold)
  • macro (vjoy press/release/pause steps) -> Macro
  • temporary-mode-switch -> a Shift-style condition on every input the target mode overrides
• Anything without a MIM equivalent is skipped and reported back in a warnings list after import, not silently dropped: custom bezier response curves (deadzone is still imported), axis-to-mouse output, keyboard steps inside a Macro, permanent mode cycling, text-to-speech, hat-to-vJoy-hat remapping.
• New gremlin:pick-import-file IPC handler just reads the raw file; XML parsing happens in the renderer via the native DOMParser, no new dependency.

Test plan

• Imported a real, in-use Gremlin profile (multiple devices, multiple modes, Tempo containers, a Macro with vJoy+keyboard steps) against real VKB hardware.
• Confirmed imported button/axis remaps produce the correct vJoy output live (verified against Windows' Game Controllers properties panel).
• Confirmed unsupported constructs show up in the post-import warning list instead of failing silently.