cfg: use %appdata%\spice2x for new config files (#300)

## Link to GitHub Issue, if one exists
n/a

## Description of change

For JSON config files of the following features:

* patch manager
* screen resize
* IIDX camera hook
* card manager

when saving a new file, store them in %appdata%\spice2x instead of
%appdata%.

On load:
1. If the JSON file exists in %appdata%\spice2x, use that (new path)
1. If the JSON file exists in %appdata%, continue to use that (legacy
path)

It's common for people to have mixed versions of spicetools/spice2x so
we'll continue to read from the %appdata% root if the files are there,
but with a preference for the new path. We will not forcibly move files.

spicetools.xml will continue to live in the %appdata% root. Moving this
will confuse a lot of people, so I'm avoiding this.

Also, this fixes `-patchcfgpath` and `-resizecfgpath` to create
directories as needed (previously the parent directory must have existed
first)

## Testing
Tested -

* existing config files are continued to be read from %appdata%
* new files get created in %appdata%\spice2x\... (both in spicecfg and
in overlay)
* can provide custom path for `-patchcfgpath` `-resizecfgpath` and
observe directories + file created in custom path, try absolute or local
relative paths

src/spice2x/util/fileutils.h

@@ -33,4 +33,7 @@ namespace fileutils {
     std::string text_read(const std::filesystem::path &file_path);
     bool bin_write(const std::filesystem::path &path, uint8_t *data, size_t len);
     std::vector<uint8_t> *bin_read(const std::filesystem::path &path);
+
+    std::filesystem::path get_config_file_path(const std::string module, const std::string filename, bool* file_exists=nullptr);
+    bool write_config_file(const std::string_view &module, const std::filesystem::path path, std::string text);
 }