[openpanel] Windows behaviour

[nuoun]

[openpanel] in current nightly on Win 10 always seems to open plugdata's program files directory. Would probably be safer to go to the Documents folder at least cause while I can't reproduce it, opening program files folders did seem to trigger some heuristic virus analysis stuff in Windows Defender on Win 10 the first time it happened.

Would be nice if it could either go at least to the Documents folder or the current patch folder (and as already was suggested in the improvements thread remembering the last folder it opened would be great for QoL)

Also sending a dirname as a symbol always seems to be considered as an absolute path making that mostly unusable for shared patches.

Edit: Spoke too soon, on linux it also sees every symbol dir name as an absolute path so that's consistent at least.