umu: temporary overrides for backwards compatibility with existing um…

…u installations

To be able to test this scout/soldier runtimes need to be copied from a Steam installation
```sh
cp ~/.local/share/Steam/steamapps/common/SteamLinuxRuntime ~/.local/share/umu/scout -r
cp ~/.local/share/Steam/ubuntu12_32/steam-runtime ~/.local/share/umu/scout/ -r
cp ~/.local/share/Steam/ubuntu12_32/steam-runtime.tar.xz.checksum ~/.local/share/umu/scout/ -r
cp ~/.local/share/Steam/steamapps/common/SteamLinuxRuntime_soldier/ ~/.local/share/umu/soldier -r
```

To run an application with `scout-on-soldier`
```sh
UMU_LOG=1 GAMEID=0 WINEPREFIX=~/Wine/umu/ PROTONPATH=scout umu-run <app>
```

umu/umu_consts.py

@@ -109,6 +109,9 @@ def __post_init__(self) -> None:  # noqa: D105
             return
         if self.path is None:
             self.path = UMU_LOCAL.joinpath(self.name)
+        # Temporary override for backwards compatibility
+        if self.version == "steamrt3":
+            self.path = UMU_LOCAL
 
 
 RUNTIME_VERSIONS = {

umu/umu_util.py

@@ -364,6 +364,9 @@ def command(self, verb: str) -> list[str]:
         """Return the tool specific entry point."""
         tool_path = os.path.normpath(self.tool_path)
         cmd = "".join([shlex.quote(tool_path), self.tool_manifest["commandline"]])
+        # Temporary override for backwards compatibility
+        if self.tool_path == str(UMU_LOCAL):
+            cmd = cmd.replace("_v2-entry-point", "umu")
         cmd = cmd.replace("%verb%", verb)
         return shlex.split(cmd)