wasm-wave: Pretty printing

I would love to pretty print WAVE text records over multiple lines, like Rust's `{:#?}` formatting.

Start by locating the wasm-wave WAVE text-record formatter and any existing formatting tests in the Rust workspace. Define the expected multiline output from Rust-style `{:#?}` behavior, add coverage for pretty printing, and verify the formatting behavior with the relevant test suite.

Written by the indexing model from the issue text.