perf(packages/codegen): `printNonNegativeFloat` write mapping directly (#25968)

Small perf optimization and code simplification.

`printNonNegativeFloat` previously passed the `node` parameter through a long chain of helper functions, so that they could call `writeWithMap` with `node` on their first write.

Instead create the sourcemapping at the start of the chain, so there's no need to pass `node` down and helpers can just use `write` / `writeLast`.