test(perry): refresh issue_6559 fast-json fixture for unbound method semantics

[proggeramlug]

Release v0.5.1519 server preflight on exact release commit 0ba0aa5 found that crates/perry/tests/issue_6559_dyn_function_interpreter.rs::fast_json_stringify_shape_end_to_end fails with TypeError: quote is not a function.

The fixture defines serializer.asString as method shorthand using this.quote, then generated code destructures const { asString } = serializer and calls asString as a free function. Per JavaScript semantics that call has no serializer receiver. Commit #9134 made method shorthand use dynamic this correctly, exposing the stale fixture assumption.

Acceptance:

• Make the fixture model an explicitly bound serializer helper, or otherwise match the real captured library shape.
• Keep the dynamic new Function interpreter path exercised.
• Verify the full issue_6559_dyn_function_interpreter integration target passes on Linux with the release runtime.