Instead of logging them as "wasm-unnamed" functions, log them as
"wasm-to-js", and append the signature.

This moves and generalizes the {AppendSignature} method that was already
used to produce the signature string for other wrappers.

R=jkummerow@chromium.org

Bug: chromium:1029470
Change-Id: Ic911cb19a49dcbc332bf5a4aa195107522ac6945
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1946350
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65287}