neovim: update tests to work with latest nixpkgs

Since https://github.com/NixOS/nixpkgs/pull/495392, the wrapper doesn't
create provider executables along with the neovim wrapper. They still
exist but at locations indicated by the g:XXX_provider_host variable.

tests/modules/programs/neovim/wrapper-args.nix

@@ -55,9 +55,20 @@ in
     assertNeovimExpr() {
         local var_name="$1"
         local expected_pattern="$2"
-        if ! nvim -i NONE --headless --cmd "echo $var_name" +q! 2>&1 | grep "$expected_pattern" ; then
-          fail "Provider $var_name doesn't match expected pattern '$expected_pattern'"
+        local output=$(nvim -i NONE --headless --cmd "echo $var_name" +q! 2>&1)
+        local exit_code=$?
+
+        if [ $exit_code -ne 0 ]; then
+          echo "neovim command failed with code: $exit_code and output:"
+          fail "$output"
+        elif ! grep "$expected_pattern" "$output" ; then
+          echo "Provider $var_name doesn't match expected pattern '$expected_pattern'"
+          echo "Output:"
+          fail "$output"
         fi
+
+        # assuming we enabled all providers
+        assertFileExists "$output"
     }
 
     # Ensure the main binary exists
@@ -67,20 +78,16 @@ in
     assertBinaryContains "$nvimBin" "-my-suffix/rplugin.vim"
 
     # 2. withPerl: Check if nvim-perl binary exists and host prog is set
-    assertFileExists "home-path/bin/nvim-perl"
-    assertNeovimExpr "g:perl_host_prog" "nvim-perl"
+    assertNeovimExpr "g:perl_host_prog" "perl"
 
     # 3. withPython3: Check if nvim-python3 binary exists and host prog is set
-    assertFileExists "home-path/bin/nvim-python3"
     assertNeovimExpr "g:python3_host_prog" "python3"
 
     # 4. withRuby: Check if nvim-ruby binary exists, GEM_HOME and host prog are set
-    assertFileExists "home-path/bin/nvim-ruby"
     assertBinaryContains "$nvimBin" "GEM_HOME="
     assertNeovimExpr "g:ruby_host_prog" "ruby"
 
     # 5. withNodeJs: Check if nvim-node binary exists and host prog is set
-    assertFileExists "home-path/bin/nvim-node"
     assertNeovimExpr "g:node_host_prog" "node"
 
     # 6. waylandSupport: Check for wl-clipboard path in wrapper's PATH modification