Pass .RenderShortcodes' Page to render hooks as .PageInner

The main use case for this is to resolve links and resources (e.g. images) relative to the included `Page`.

A typical `include` would similar to this:

```handlebars
{{ with site.GetPage (.Get 0) }}
  {{ .RenderShortcodes }}
{{ end }}
```

And when used in a Markdown file:

```markdown
{{% include "/posts/p1" %}}
```

Any render hook triggered while rendering `/posts/p1` will get `/posts/p1` when calling `.PageInner`.

Note that

* This is only relevant for shortcodes included with `{{%` that calls `.RenderShortcodes`.
* `.PageInner` is available in all render hooks that, before this commit, received `.Page`.
* `.PageInner` will fall back to the value of `.Page` if not relevant and will always have a value.

Fixes #12356

markup/goldmark/hugocontext/hugocontext_test.go

@@ -0,0 +1,34 @@
+// Copyright 2024 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hugocontext
+
+import (
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+)
+
+func TestWrap(t *testing.T) {
+	c := qt.New(t)
+
+	b := []byte("test")
+
+	c.Assert(string(Wrap(b, 42)), qt.Equals, "{{__hugo_ctx pid=42}}\ntest{{__hugo_ctx/}}\n")
+}
+
+func BenchmarkWrap(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		Wrap([]byte("test"), 42)
+	}
+}