audio: simplify ASIO backend conversion (#560)

## Link to GitHub Issue or related Pull Request, if one exists

## Description of change
Deprecate backend conversion options and replace with one unified option
for enabling WASAPI exclusive conversion to ASIO.

The new option takes in a string (ASIO driver name) and when filled out,
it automatically enables the ASIO backend.

This is to avoid confusion that was caused by the previous option - the
fact that it was split into two (one to enable the conversion, another
to optionally pick which ASIO driver to use) and that user needed to
specify an integer as opposed to the driver name.

## Testing
Tested on IIDX33. Old options should continue to work.

src/spice2x/launcher/options.cpp

@@ -1742,11 +1742,13 @@ static const std::vector<OptionDefinition> OPTION_DEFINITIONS = {
         .category = "Audio (Hacks)",
     },
     {
-        .title = "Spice Audio Hook Backend",
+        // AudioBackend
+        .title = "Spice Audio Hook Backend (DEPRECATED - use -asioconvert instead)",
         .name = "audiobackend",
         .desc = "Selects the audio backend to use when spice audio hook is enabled, overriding exclusive WASAPI. "
             "Does nothing for games that do not output to exclusive WASAPI.",
         .type = OptionType::Enum,
+        .hidden = true,
         .category = "Audio",
         .elements = {
             {"asio", "ASIO"},
@@ -1754,10 +1756,23 @@ static const std::vector<OptionDefinition> OPTION_DEFINITIONS = {
         },
     },
     {
-        .title = "Spice Audio Hook ASIO Driver ID",
+        // AsioDriverId
+        .title = "Spice Audio Hook ASIO Driver ID (DEPRECATED - use -asioconvert instead)",
         .name = "asiodriverid",
         .desc = "Selects the ASIO driver id to use when Spice Audio Backend is set to ASIO.",
         .type = OptionType::Integer,
+        .hidden = true,
+        .category = "Audio",
+    },
+    {
+        // AsioDriverName
+        .title = "WASAPI Exclusive to ASIO Conversion",
+        .name = "asioconvert",
+        .desc = "Converts WASAPI Exclusive audio output to ASIO. Value here should match registry key under HKLM\\SOFTWARE\\ASIO\\\n\n"
+            "Use this if the game is configured to use WASAPI Exclusive but you want to use your ASIO driver instead.\n\n"
+            "This should only be used as last resort if your audio device does not support WASAPI Exclusive.\n\n"
+            "Does nothing for games that do not output to exclusive WASAPI.",
+        .type = OptionType::Text,
         .category = "Audio",
     },
     {