[code-reflection] RFR: Transformation API changes

[Paul Sandoz]

On Mon, 14 Jul 2025 20:47:59 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:

> Move transformation of a `Body` starting at a `Block.Builder` to `OpTransformer`, which now has three methods, default method `acceptBody` calls default method `acceptBlock`, which in turn calls abstract method `acceptOp`.
> 
> Simplify the body accepting methods on `Block.Builder` which now defer to `OpTransformer.acceptBody`. Those methods are responsible for rebinding the `Block.Builder` and passing the rebound result to `acceptBody`.

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PR Review: https://git.openjdk.org/babylon/pull/494#pullrequestreview-3080705847