Provide a Pkl renderer

There should be a renderer that renders Pkl output.

Use-cases:
* Eschew the need to create converter modules like https://pkl-lang.org/package-docs/pkg.pkl-lang.org/pkl-pantry/k8s.contrib/current/convert/index.html
* Ability to programmatically rewrite Pkl using Pkl itself

Imagined usage:

```pkl
output {
renderer = new PklRenderer {}
value = someValue
}
```

Rendered module should be importable in Pkl, and be logically equivalent to `someValue`.

Output would not retain programming constructs like for/when/amends chains.

The issue names no repository files or tests; start by locating the output and renderer entry points and reviewing how existing Pkl outputs are produced. Use the linked converter-module example as context. Done means a PklRenderer can emit importable Pkl that is logically equivalent to the input value without retaining for, when, or amends constructs.

Written by the indexing model from the issue text.