CI: Fix running the workaround for `NuGet-Migrations` issue (#85692)

CI: Fix running the workaround for `NuGet-Migrations` issue (#85692)

* CI: Fix running the workaround for `NuGet-Migrations` issue

The workaround adds:

`(CONSOLE_TEMP_DIR="%24(mktemp -d)" %3B "$DOTNET_ROOT/dotnet" new console -o "$CONSOLE_TEMP_DIR" %3B rm -rf "$CONSOLE_TEMP_DIR") || true`

which uses `$DOTNET_ROOT/dotnet`. But this is set for `HelixPreCommand`
which runs *before* `DOTNET_ROOT` is set.

Instead, use `HelixCommandPrefixItem`.

* rename HelixCommandPrefixItem to HelixCommandPrefixEnvVarItem

* Fix in helixpublishwitharcade.proj also

* Add the workaround for legacy payloads also, which includes wasm runtime tests

* fix typo