game: cleanup gk's CLI documentation (#2189)

An attempt to cleanup the last CLI interface we have left to cleanup. 
- `gk` args now follow the typical convention ie. `--proj-path` instead
of `-proj-path`.
- args that are passed through to the rest of the application / the
game's runtime use the typical convention of following a `--`
- I'm thinking some args shouldn't be handled at this level ie
(`-nodisplay`, `-vm`, `-novm` or `-jak2`) These could be better
documented as legitimate flags and passed in via a nice struct. They
don't seem to be used in `InitParams` but I'll triple check.

There's a temporary shim here so there is no coupled release with the
launcher (right now it executes `gk` with a few args). So I just change
the old args into the new format. After one release cycle, I can change
it in the launcher and delete it here.

I am unsure if this will break the bash shellscript usages -- not sure
which args were usually passed into `$@`


![image](https://user-images.githubusercontent.com/13153231/222035309-b6601719-cdc9-40ee-b36e-e4b135d3f128.png)

game/kernel/jak2/kmachine.cpp

@@ -152,17 +152,17 @@ void InitParms(int argc, const char* const* argv) {
     // new for jak 2
     if (arg == "-user") {
       i++;
-      std::string levelName = argv[i];
-      Msg(6, "dkernel: user %s\n", levelName.c_str());
-      kstrcpy(DebugBootUser, levelName.c_str());
+      std::string userName = argv[i];
+      Msg(6, "dkernel: user %s\n", userName.c_str());
+      kstrcpy(DebugBootUser, userName.c_str());
     }
 
     // new for jak 2
     if (arg == "-art") {
       i++;
-      std::string levelName = argv[i];
-      Msg(6, "dkernel: art-group %s\n", levelName.c_str());
-      kstrcpy(DebugBootArtGroup, levelName.c_str());
+      std::string artGroupName = argv[i];
+      Msg(6, "dkernel: art-group %s\n", artGroupName.c_str());
+      kstrcpy(DebugBootArtGroup, artGroupName.c_str());
       kstrcpy(DebugBootMessage, "art-group");
     }